Question

Japan and Fiji are both island countries. The population of Japan is approximately 1.3*10^8. The population of Fiji is approximately 8.8*10^5. Which is the best estimate of how many times as great the population of Japan is as Fiji?
A about 1.5 times as great
B about 15 times as great
C about 150 times as great
D about 1500 times as great

Answer 1

What we'll do is divide 1.3 x 10^8 by 8.8 x 10^5:
1.3 x 10^8 / 8.8 x 10^5

We can rewrite 1.3 x 10^8 such that the exponent of 10 is 5. To do this, move the decimal point 3 places to the right. Why 3 places? It's because 8-5 = 3:
1.3 x 10^8 = 1300 x 10^5

Then,
1300 x 10^5 / 8.8 x 10^5
We can cancel out the 10^5 from numerator and denominator:
1300 / 8.8
Note that 8.8 is close to 10. Estimating,
1300 / 10 = 130

The closest choice to 130 is letter C - about 150 times.

hope this helps~ `u`