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Find two numbers such that the sum of thrice the first number and twice the second number is 102. Also five times the first number exceeds thrice the second number by 18. Find the numbers. - Mathematics

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Question

Find two numbers such that the sum of thrice the first number and twice the second number is 102. Also, five times the first number exceeds thrice the second number by 18. Find the numbers.

Sum
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Solution

Here, let the two numbers be:

First number = x

Second number = y

According to the given conditions:

(1) Thrice the first + twice the second = 102,

3x + 2y = 102     ...(1)

(2) Five times the first exceeds thrice the second by 18,

5x = 3y + 18     ...(2)

`x = (3y + 18)/5`      ...(3)

Now, substituting equation (3) into equation (1):

`3((3y + 18)/5) + 2y = 102`

`(9y + 54)/5 + 2y = 102`

Multiplying the entire equation by 5:

`5((9y + 54)/5) + 5(2y) = 5(102)`

9y + 54 + 10y = 510

9y + 10y = 510 − 54

19y = 456

y = `456/19`

∴ y = 24

Thus, substituting y = 24 into equation (3):

`x = (3(24) + 18)/5`

`x = (72 + 18)/5`

`x = 90/5`

∴ x = 18

Hence, the numbers are 18 and 24.

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Chapter 5: Simultaneous Linear Equations - EXERCISE 5B [Page 59]

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B Nirmala Shastry Mathematics [English] Class 9 ICSE
Chapter 5 Simultaneous Linear Equations
EXERCISE 5B | Q 3. | Page 59
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