Advertisements
Advertisements
Question
So Anar also tried many different ways to make a boundary for 800 square meters of land.
He made rectangles A, B, and C of different sizes. Find out the length of the boundary of each. How much gold wire will he get for these rectangles?
- A
Gold wire for A = _________ metres - B
Gold wire for B = _________ metres - C
Gold wire for C = __________ metres
But then Anar made an even longer rectangle... See how long!
- D
So he will get __________ metres of gold wire!!
Advertisements
Solution
Area of 30 m × 20 m rectangle = 600 square metres
Its area is larger than the area of the first rectangle.
The other rectangles that he can make with 100 metres of wire are
40 m × 10 m,
48 m × 2 m,
49 m × 1 m,
45 m × 5 m
- A
As the area of a rectangle, A is shown as 40 m × 20 m.
So, the length of rectangle = 40 m
Width of rectangle = 20 m
Gold wire for A
= 40 + 20 + 40 + 20
= 120 metres - B
As the area of rectangle B is shown as 80 m × 10 m.
So, the length of rectangle = 80 m
Width of rectangle = 10 m
Gold wire for B
= 80 + 10 + 80 + 10
= 180 metres - C
As the area of rectangle C is shown as 800 m × 1 m.
So, the length of rectangle = 800 m
Width of rectangle = 1 m
Gold wire for C
= 800 + 1 + 800 + 1
= 1602 metres - D
As the area of rectangle D is shown as 8000 m × 0.1 m.
So, the length of rectangle = 8000 m
Width of rectangle = 0.1 m
Gold wire for C
= 8000 + 0.1 + 8000 + 0.1
= 16000 + 0.2
= 16000.2 metres.
So, he will get 16000.2 metres of gold wire!!
APPEARS IN
RELATED QUESTIONS
The principle of ‘parallax’ in section 2.3.1 is used in the determination of distances of very distant stars. The baseline AB is the line joining the Earth’s two locations six months apart in its orbit around the Sun. That is, the baseline is about the diameter of the Earth’s orbit ≈ 3 × 1011m. However, even the nearest stars are so distant that with such a long baseline, they show parallax only of the order of 1” (second) of arc or so. A parsec is a convenient unit of length on the astronomical scale. It is the distance of an object that will show a parallax of 1” (second) of arc from opposite ends of a baseline equal to the distance from the Earth to the Sun. How much is a parsec in terms of meters?
Just as precise measurements are necessary in science, it is equally important to be able to make rough estimates of quantities using rudimentary ideas and common observations. Think of ways by which you can estimate the following (where an estimate is difficult to obtain, try to get an upper bound on the quantity):-
the number of air molecules in your classroom.
500 gm = ______ kilogram.
Match the following.
| 1. | Length of the fore arm | metre |
| 2. | SI unit of length | second |
| 3. | Nano | 103 |
| 4. | SI Unit of time | 10–9 |
| 5. | Kilo | Cubit |
Metre is the unit of ______.
Have you seen frogs? Where? How many different types of frogs have you seen? Are all the frogs of the same length? Here are two interesting examples.
Guess the lengths to draw these things. Ask your friend to draw the same. After you make the drawing use a scale to measure the length. Whose drawing showed a better guess?
| Guess its length and draw |
Measure of your drawing |
Measure of your friend’s drawing |
| An ant of length less than 1 cm |
||
| Pencil of length about 7 cm |
||
| A glass 11 cm high with water up to 5 cm |
||
| A bangle of perimeter 20 cm |
||
| A curly hair of length 16 cm |
How many stamps are needed to cover the rectangle?
How close was your earlier guess? Discuss.
You can play this game on the ground. Make two squares of one square meter each. Divide your class into two teams. Ready to play!
- How many of you can stand in it?
There are two beautiful lakes near a village. People come for boating and picnics in both the lakes. The village Panchayat is worried that with the noise of the boats the birds will stop coming. The Panchayat wants motorboats in only one lake. The other lake will be saved for the birds to make their nests.
- How many kilometers long is the actual boundary of lake B?
Match the following:
| Prefix | Symbol | ||
| a. | Centi | i. | k |
| b. | Nano | ii. | c |
| c. | Mili | iii. | n |
| d. | Kilo | iv. | m |
Give some examples of larger length measures.
What is the unit of measurements of very small lengths?
What is the unit of length?
The SI unit of mass is kg.
How many astronomical units (A.U.) make 1 parsec?
In the parallax formula D = b/θ, what must be true about the angle θ for the calculation to be correct?
