easy way

blaster wrote:Which of the following fractions is equal ot the decimal 0.0625

A) 5/8
B) 3/8
C) 1/16
D) 1/18
E) 3/80

is there easy way to solve this kind of question?

There are a few ways to do this kind of question. I'd personally likely go with Dana's approach, but with the answer choices above, there are other options. 5/8 and 3/8 are clearly larger than 0.1, so cannot be correct. 3/80 is between 3/100 = 0.03 and 3/50 = 0.06, so is too small. 1/18 is a reduced fraction with a prime divisor different from 2 or 5 in its denominator, so it would yield a repeating decimal, so can't possibly be equal to 0.0625. That only leaves 1/16 as a possibility.

You might also be able to use a few decimals you already know to work out the decimal equivalents of the fractions above. For example, 1/4 is equal to 0.25; 1/8 is half of 1/4, so must equal half of 0.25, or 0.125. So 3/8 is three times 0.125, or 0.375, and 3/80 is one tenth of that, so is equal to 0.0375. Similarly, we can find that 5/8 = 0.625. To find the decimal for 1/18, we can use the fact that 1/3 = 0.333..., and since 1/9 is one third of 1/3, 1/9 must be equal to 1/3 of 0.333..., so 1/9 = 0.111... Now, 1/18 is one half of that, so 1/18 = 0.0555....