Question

9. The approximate circumferences of Earth

Answer 1

Answer and explanation:

1) Given : Circumference of Earth $C_E= 365,882\ km$

Circumference of Saturn $C_S= 4.01\times 10^4\ km$

To find : How many times  greater is the circumference of Saturn than  the circumference of Earth?

Solution :

Let x be the number of times greater is the circumference of Saturn than  the circumference of Earth.

According to question,

$x=\frac{C_E}{C_S}$

$x=\frac{365882}{4.01\times 10^4}$

$x=\frac{365882}{40100}$

$x=9.124$

Therefore, 9.124 times  greater is the circumference of Saturn than  the circumference of Earth.

2) Number  0.037854921

Estimate to the nearest hundredth.

The hundredth number is 3 and thousandth number is 7.

As thousandth number 7 is greater than 5.

So, hundredth number is added by 1 and rest became zero.

i.e. $0.037854921\approx 0.04$

3) Compare the numbers $6 \times 10{-6}$ and $2\times 10{-8}$

$6 \times 10{-6}=\frac{6}{1000000}$

$2\times 10{-8}=\frac{2}{100000000}=\frac{0.02}{1000000}$

As the denominator is same compare the numerator,

0.02<6 or 6>0.02

So, $6 \times 10{-6}>2\times 10{-8}$

Therefore, $6 \times 10{-6}$ is greater than $2\times 10{-8}$