Tamil Nadu Board of Secondary EducationSSLC (English Medium) Class 8th

# Tamil Nadu Board Samacheer Kalvi solutions for Class 8th Mathematics Answers Guide chapter 4 - Life Mathematics [Latest edition]

#### Chapters ## Chapter 4: Life Mathematics

Exercise 4.1Exercise 4.2Exercise 4.3Exercise 4.4Exercise 4.5
Exercise 4.1 [Page 125]

### Tamil Nadu Board Samacheer Kalvi solutions for Class 8th Mathematics Answers Guide Chapter 4 Life MathematicsExercise 4.1 [Page 125]

#### Fill in the blanks:

Exercise 4.1 | Q 1. (i) | Page 125

If 30% of x is 150, then x is _______

Exercise 4.1 | Q 1. (ii) | Page 125

2 minutes is _______ % to an hour

Exercise 4.1 | Q 1. (iii) | Page 125

If x % of x = 25, then x = _______

Exercise 4.1 | Q 1. (iv) | Page 125

In a school of 1400 students, there are 420 girls. The percentage of boys in the school is _______

Exercise 4.1 | Q 1. (v) | Page 125

0.5252 is _______ %

Exercise 4.1 | Q 2. (i) | Page 125

Rewrite the underlined part using percentage language.

One half of the cake is distributed to the children

Exercise 4.1 | Q 2. (ii) | Page 125

Rewrite the underlined part using percentage language.

Aparna scored 7.5 points out of 10 in a competition

Exercise 4.1 | Q 2. (iii) | Page 125

Rewrite the underlined part using percentage language.

The statue was made of pure silver

Exercise 4.1 | Q 2. (iv) | Page 125

Rewrite the underlined part using percentage language.

48 out of 50 students participated in sports

Exercise 4.1 | Q 2. (v) | Page 125

Rewrite the underlined part using percentage language.

Only 2 persons out of 3 will be selected in the interview

Exercise 4.1 | Q 3 | Page 125

48 is 32% of which number?

Exercise 4.1 | Q 4 | Page 125

What is 25% of 30% of 400?

Exercise 4.1 | Q 5 | Page 125

If a car is sold for ₹ 2,00,000 from its original price of ₹ 3,00,000, then find the percentage of decrease in the value of the car Exercise 4.1 | Q 6 | Page 125

If the difference between 75% of a number and 60% of the same number is 82.5, then find 20% of that number

Exercise 4.1 | Q 7 | Page 125

A number when increased by 18% gives 236. Find the number

Exercise 4.1 | Q 8 | Page 125

A number when decreased by 20% gives 80. Find the number

Exercise 4.1 | Q 9 | Page 125

A number is increased by 25% and then decreased by 20%. Find the percentage change in that number

Exercise 4.1 | Q 10 | Page 125

The ratio of boys and girls in a class is 5 : 3. If 16% of boys and 8% of girls failed in an examination, then find the percentage of passed students.

#### Objective Type Questions

Exercise 4.1 | Q 11 | Page 125

12% of 250 litre is the same as ________ of 150 litre

• 10%

• 15%

• 20%

• 30%

Exercise 4.1 | Q 12 | Page 125

If three candidates A, B and C in a school election got 153,245 and 102 votes respectively, then the percentage of votes got by the winner is _____________

• 48%

• 49%

• 50%

• 45%

Exercise 4.1 | Q 13 | Page 125

15% of 25% of 10000 = ___________

• 375

• 400

• 425

• 475

Exercise 4.1 | Q 14 | Page 125

When 60 is subtracted from 60% of a number to give 60, the number is

• 60

• 100

• 150

• 200

Exercise 4.1 | Q 15 | Page 125

If 48% of 48 = 64% of x, then x =

• 64

• 56

• 42

• 36

Exercise 4.2 [Pages 130 - 132]

### Tamil Nadu Board Samacheer Kalvi solutions for Class 8th Mathematics Answers Guide Chapter 4 Life MathematicsExercise 4.2 [Pages 130 - 132]

#### Fill in the blanks:

Exercise 4.2 | Q 1. (i) | Page 130

Loss or gain percentage is always calculated on the ________

Exercise 4.2 | Q 1. (ii) | Page 130

A mobile phone is sold for ₹ 8400 at a gain of 20%. The cost price of the mobile phone is ________

Exercise 4.2 | Q 1. (iii) | Page 131

An article is sold for ₹ 555 at a loss of 7 1/2%. The cost price of the article is ________

Exercise 4.2 | Q 1. (iv) | Page 131

A mixer grinder marked at ₹ 4500 is sold for ₹ 4140 after discount. The rate of discount is __________

Exercise 4.2 | Q 1. (v) | Page 131

The total bill amount of a shirt costing ₹ 575 and a T-shirt costing ₹ 325 with GST of 5% is _______

Exercise 4.2 | Q 2 | Page 131

If selling an article for ₹ 820 causes 10% loss on the selling price, then find its cost price

Exercise 4.2 | Q 3 | Page 131

If the profit earned on selling an article for ₹ 810 is the same as loss on selling it for ₹ 530, then find the cost price of the article.

Exercise 4.2 | Q 4 | Page 131

If the selling price of 10 rulers is the same as the cost price of 15 rulers, then find the profit percentage

Exercise 4.2 | Q 5 | Page 131

Some articles are bought at 2 for ₹ 15 and sold at 3 for ₹ 25. Find the gain percentage

Exercise 4.2 | Q 6 | Page 131

By selling a speaker for ₹ 768, a man loses 20%. In order to gain 20%, how much should he sell the speaker? Exercise 4.2 | Q 7. (i) | Page 131

Find the unknowns x, y and z.

 Name of the item Marked Price Selling Price Discount Book ₹ 225 x 8%
Exercise 4.2 | Q 7. (ii) | Page 131

Find the unknowns x, y and z.

 Name of the item Marked Price Selling Price Discount LED TV y ₹ 11970 5%
Exercise 4.2 | Q 7. (iii) | Page 131

Find the unknowns x, y and z.

 Name of the item Marked Price Selling Price Discount Digital clock ₹ 750 ₹ 615 z
Exercise 4.2 | Q 8. (i) | Page 131

Find the total bill amount for the data given below:

 Name of the item Marked Price Discount GST School bag ₹ 500 5% 12%
Exercise 4.2 | Q 8. (ii) | Page 131

Find the total bill amount for the data given below:

 Name of the item Marked Price Discount GST Hair dryer ₹ 2000 10% 28%
Exercise 4.2 | Q 9. (i) | Page 131

A branded Air-Conditioner (AC) has a marked price of ₹ 38000. There is a condition given for the customer.

Selling Price is the same ₹ 38000 but with attractive gifts worth ₹ 3000 Exercise 4.2 | Q 9. (ii) | Page 131

A branded Air-Conditioner (AC) has a marked price of ₹ 38000. There is a condition given for the customer.

Discount of 8% on the marked price but no free gifts. Exercise 4.2 | Q 10 | Page 132

If a mattress is marked for ₹ 7500 and is available at two successive discount of 10% and 20%, find the amount to be paid by the customer

#### Objective Type Questions

Exercise 4.2 | Q 11 | Page 132

A fruit vendor sells fruits for ₹ 200 gaining ₹ 40. His gain percentage is

• 20%

• 22%

• 25%

• 16 2/3%

Exercise 4.2 | Q 12 | Page 132

By selling a flower pot for ₹ 528, a woman gains 20%. At what price should she sell it to gain 25%?

• ₹ 500

• ₹ 550

• ₹ 553

• ₹ 573

Exercise 4.2 | Q 13 | Page 132

A man buys an article for ₹ 150 and makes overhead expenses which are 12% of the cost price. At what price must he sell it to gain 5%?

• ₹ 180

• ₹ 168

• ₹ 176.40

• ₹ 88.20

Exercise 4.2 | Q 14 | Page 132

What is the marked price of a hat which is bought for ₹ 210 at 16% discount?

• ₹ 243

• ₹ 176

• ₹ 230

• ₹ 250

Exercise 4.2 | Q 15 | Page 132

The single discount in % which is equivalent to two successive discounts of 20% and 25% is

• 40%

• 45%

• 5%

• 22.5%

Exercise 4.3 [Pages 138 - 140]

### Tamil Nadu Board Samacheer Kalvi solutions for Class 8th Mathematics Answers Guide Chapter 4 Life MathematicsExercise 4.3 [Pages 138 - 140]

#### Fill in the blanks:

Exercise 4.3 | Q 1. (i) | Page 138

The compound interest on ₹ 5000 at 12% p.a for 2 years, compounded annually is ___________

Exercise 4.3 | Q 1. (ii) | Page 138

The compound interest on ₹ 8000 at 10% p.a for 1 year, compounded half yearly is ____________

Exercise 4.3 | Q 1. (iii) | Page 138

The annual rate of growth in population of a town is 10%. If its present population is 26620, then the population 3 years ago was _________

Exercise 4.3 | Q 1. (iv) | Page 138

If the compound interest is calculated quarterly, the amount is found using the formula __________

Exercise 4.3 | Q 1. (v) | Page 138

The difference between the C.I and S.I for 2 years for a principal of ₹ 5000 at the rate of interest 8% p.a is ___________

#### Say True or False

Exercise 4.3 | Q 2. (i) | Page 139

Depreciation value is calculated by the formula, "P"(1 - "r"/100)^"n"

• True

• False

Exercise 4.3 | Q 2. (ii) | Page 139

If the present population of a city is P and it increases at the rate of r% p.a, then the population n years ago would be "P"(1 + "r"/100)^"n"

• True

• False

Exercise 4.3 | Q 2. (iii) | Page 139

The present value of a machine is ₹ 16800. It depreciates at 25% p.a. Its worth after 2 years is ₹ 9450

• True

• False

Exercise 4.3 | Q 2. (iv) | Page 139

The time taken for ₹ 1000 to become ₹ 1331 at 20% p.a, compounded annually is 3 years

• True

• False

Exercise 4.3 | Q 2. (v) | Page 139

The compound interest on ₹ 16000 for 9 months at 20% p.a, compounded quarterly is ₹ 2522

• True

• False

Exercise 4.3 | Q 3 | Page 139

Find the compound interest on ₹ 3200 at 2.5% p.a for 2 years, compounded annually

Exercise 4.3 | Q 4 | Page 139

Find the compound interest for 2 1/2 years on ₹ 4000 at 10% p.a, if the interest is compounded yearly

Exercise 4.3 | Q 5 | Page 139

A principal becomes ₹ 2028 in 2 years at 4% p.a compound interest. Find the principal

Exercise 4.3 | Q 6 | Page 139

In how many years will ₹ 3375 become ₹ 4096 at 13 1/3 p.a if the interest is compounded half-yearly?

Exercise 4.3 | Q 7 | Page 139

Find the C.I. on ₹ 15000 for 3 years if the rates of interest are 15%, 20% and 25% for the I, II and III years respectively

Exercise 4.3 | Q 8 | Page 139

Find the difference between C.I and S.I on ₹ 5000 for 1 year at 2% p.a, if the interest is compounded half yearly

Exercise 4.3 | Q 9 | Page 139

Find the rate of interest if the difference between C.I and S.I on ₹ 8000 compounded annually for 2 years is ₹ 20

Exercise 4.3 | Q 10 | Page 139

Find the principal if the difference between C.I and S.l on it at 15% p.a for 3 years is ₹ 1134

#### Objective Type Questions

Exercise 4.3 | Q 11 | Page 139

The number of conversion periods in a year, if the interest on a principal is compounded every two months is ___________

• 2

• 4

• 6

• 12

Exercise 4.3 | Q 12 | Page 139

The time taken for ₹ 4400 to become ₹ 4851 at 10%, compounded half yearly is _______

• 6 months

• 1 year

• 1 1/2 years

• 2 years

Exercise 4.3 | Q 13 | Page 139

The cost of a machine is ₹ 18000 and it depreciates at 16 2/3 % annually. Its value after 2 years will be ___________

• ₹ 12000

• ₹ 12500

• ₹ 15000

• ₹ 16500

Exercise 4.3 | Q 14 | Page 140

The sum which amounts to ₹ 2662 at 10% p.a in 3 years, compounded yearly is _________

• ₹ 2000

• ₹ 1800

• ₹ 1500

• ₹ 2500

Exercise 4.3 | Q 15 | Page 140

The difference between compound and simple interest on a certain sum of money for 2 years at 2% p.a is ₹ 1. The sum of money is __________

• ₹ 2000

• ₹ 1500

• ₹ 3000

• ₹ 2500

Exercise 4.4 [Pages 150 - 151]

### Tamil Nadu Board Samacheer Kalvi solutions for Class 8th Mathematics Answers Guide Chapter 4 Life MathematicsExercise 4.4 [Pages 150 - 151]

#### Fill in the blanks:

Exercise 4.4 | Q 1. (i) | Page 150

A can finish a job in 3 days whereas B finishes it in 6 days. The time taken to complete the job working together is __________ days

Exercise 4.4 | Q 1. (ii) | Page 150

If 5 persons can do 5 jobs in 5 days, then 50 persons can do 50 jobs in _________ days

Exercise 4.4 | Q 1. (iii) | Page 150

A can do a work in 24 days. If A and B together can finish the work in 6 days, then B alone can finish the work in ________ days

Exercise 4.4 | Q 1. (iv) | Page 150

A alone can do a piece of work in 35 days. If B is 40% more efficient than A, then B will finish the work in ___________ days

Exercise 4.4 | Q 1. (v) | Page 150

A alone can do a work in 10 days and B alone in 15 days. They undertook the work for ₹ 200000. The amount that A will get is ________

Exercise 4.4 | Q 2 | Page 150

210 men working 12 hours a day can finish a job in 18 days. How many men are required to finish the job in 20 days working 14 hours a day?

Exercise 4.4 | Q 3 | Page 150

A cement factory makes 7000 cement bags in 12 days with the help of 36 machines. How many bags can be made in 18 days using 24 machines?

Exercise 4.4 | Q 4 | Page 150

A soap factory produces 9600 soaps in 6 days working 15 hours a day. In how many days will it produce 14400 soaps working 3 more hours a day?

Exercise 4.4 | Q 5 | Page 150

If 6 container lorries can transport 135 tonnes of goods in 5 days, how many more lorries are required to transport 180 tonnes of goods in 4 days?

Exercise 4.4 | Q 6 | Page 150

A can do a piece of work in 12 hours, B and C can do it 3 hours whereas A and C can do it in 6 hours. How long will B alone take to do the same work?

Exercise 4.4 | Q 7 | Page 150

A and B can do a piece of work in 12 days, while B and C can do it in 15 days where as A and C can do it in 20 days. How long would each take to do the same work?

Exercise 4.4 | Q 8 | Page 150

Carpenter A takes 15 minutes to fit the parts of a chair while Carpenter B takes 3 minutes more than A to do the same work. Working together, how long will it take for them to fit the parts for 22 chairs?

Exercise 4.4 | Q 9 | Page 151

A can do a work In 45 days. He works at it for 15 days and then, B alone finishes the remaining work in 24 days. Find the time taken to complete 80% of the work, if they work together

Exercise 4.4 | Q 10 | Page 151

A is thrice as fast as B. If B can do a piece of work in 24 days then, find the number of days they will take to complete the work together

Exercise 4.5 [Pages 151 - 152]

### Tamil Nadu Board Samacheer Kalvi solutions for Class 8th Mathematics Answers Guide Chapter 4 Life MathematicsExercise 4.5 [Pages 151 - 152]

#### Miscellaneous Practice Problems

Exercise 4.5 | Q 1 | Page 151

A fruit vendor bought some mangoes of which 10% were rotten. He sold 33 1/3% of the rest. Find the total number of mangoes bought by him initially, if he still has 240 mangoes with him Exercise 4.5 | Q 2 | Page 151

A student gets 31% marks in an examination but fails by 12 marks. If the pass percentage is 35%, find the maximum marks of the examination.

Exercise 4.5 | Q 3 | Page 151

Sultana bought the following things from a general store. Calculate the total bill amount paid by her.

(i) Medicines costing ₹800 with GST at 5% (ii) Cosmetics costing ₹ 650 with GST at 12% (iii) Cereals costing ₹900 with GST at 0% (iv) Sunglass costing ₹1750 with GST at18% (v) Air Conditioner costing ₹28500 with GST at 28% Exercise 4.5 | Q 4 | Page 151

P’s income is 25% more than that of Q. By what percentage is Q’s income less than P’s?

Exercise 4.5 | Q 5 | Page 151

Vaidegi sold two sarees for ₹ 2200 each. On one she gains 10% and on the other she loses 12%. Find her total gain or loss percentage in the sale of the sarees Exercise 4.5 | Q 6 | Page 151

If 32 men working 12 hours a day can do a work in 15 days, then how many men working 10 hours a day can do double that work in 24 days?

Exercise 4.5 | Q 7 | Page 151

Amutha can weave a saree in 18 days. Anjali is twice as good a weaver as Amutha. If both of them weave together, then in how many days can they complete weaving the saree?

Exercise 4.5 | Q 8 | Page 152

P and Q can do a piece of work in 12 days and 15 days respectively. P started the work alone and then after 3 days, Q joined him till the work was completed. How long did the work last?

#### Challenging Problems

Exercise 4.5 | Q 9 | Page 152

If the numerator of a fraction is increased by 50% and the denominator is decreased by 20%, then it becomes 3/5. Find the original fraction

Exercise 4.5 | Q 10 | Page 152

Gopi sold a laptop at 12% gain. If it had been sold for ₹ 1200 more, the gain would have been 20%. Find the cost price of the laptop Exercise 4.5 | Q 11 | Page 152

A shopkeeper gives two successive discounts on an article whose marked price is ₹ 180 and selling price is ₹ 108. Find the first discount percentage if the second discount is 25%

Exercise 4.5 | Q 12 | Page 152

Find the rate of compound interest at which a principal becomes 1.69 times itself in 2 years

Exercise 4.5 | Q 13 | Page 152

A small-scale company undertakes an agreement to make 540 motor pumps in 150 days and employs 40 men for the work. After 75 days, the company could make only 180 motor pumps. How many more men should the company employees so that the work is completed on time as per the agreement?

Exercise 4.5 | Q 14 | Page 152

P alone can do 1/2 of a work in 6 days and Q alone can do 2/3 of the same work in 4 days. in how many days will they finish 3/4 of the work, working together?

Exercise 4.5 | Q 15 | Page 152

X alone can do a piece of work in 6 days and Y alone in 8 days. X and Y undertook the work for ₹ 48000. With the help of Z, they completed the work in 3 days. How much is Z’s share?

## Chapter 4: Life Mathematics

Exercise 4.1Exercise 4.2Exercise 4.3Exercise 4.4Exercise 4.5 ## Tamil Nadu Board Samacheer Kalvi solutions for Class 8th Mathematics Answers Guide chapter 4 - Life Mathematics

Tamil Nadu Board Samacheer Kalvi solutions for Class 8th Mathematics Answers Guide chapter 4 (Life Mathematics) include all questions with solution and detail explanation. This will clear students doubts about any question and improve application skills while preparing for board exams. The detailed, step-by-step solutions will help you understand the concepts better and clear your confusions, if any. Shaalaa.com has the Tamil Nadu Board of Secondary Education Class 8th Mathematics Answers Guide solutions in a manner that help students grasp basic concepts better and faster.

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Concepts covered in Class 8th Mathematics Answers Guide chapter 4 Life Mathematics are Concept of Percent and Percentage, Concepts of Cost Price, Selling Price, Total Cost Price, and Profit and Loss, Discount, Overhead Expenses and GST, Concept of Compound Interest, Difference Between Compound Interest and Simple Interest, Compound Variation, Concept of Direct Proportion, Concept of Inverse Proportion, Time and Work.

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