10 percent of 50 percent of a number is 30 less than one quarter of the number, what's the number?

So first, we want to find the total decrease on the number.

Since it was first decreased by 50% and then 10%, we can just multiply the two together to find what 10% of 50% is. I find it easier when they're both fractions, or 1/2 and 1/10.

1/2 * 1/10 = 1/20

So one quarter is 1/4, or 5/20.

1/20 is 4/20 less then 5/20.

1/20 is 30 less then 1/4, then 4/20 must equal 30.

4/20 is also 1/5.

So just multiply 30 by 5, to get 150 as your number. (1/5 * 5 = 5/5)