Sometimes, dividing a number by a power of 10 (like 10, 100, 1000 etc.) is easy because all you need to do is move the invisible decimal place left by how many zeros you have in the power of 10. But for this question, the denominator, 100, isn’t a power of 10.

However, we can change the fraction: if the denominator is a factor of a power of 10, like 2, 4, 5, 8, 10, 16, 20, 25, 40, 50 and so on, then we can convert the fraction into one that is easy to calculate.

To do this, we need to make the denominator to a power of 10 - to make 100 a power of 10, we need to multiply by 1 (100 * 1 = 100). We multiplied the denominator by 1, so now we need to also multiply the numerator by 1 too:

$\frac{39 * 1}{100 * 1} = \frac{39}{100} = 0.39$

And finally, you get 0.39 as your answer when you convert 39/100 to a decimal.