Question

Explain why a change from 20 to 40 is a 100% increase, but a change from 40 to 20 is a 50% decrease.

Increasing 20 to 40 is the same as increasing 20 by c. So, it is a 100% increase. Decreasing 40 to 20 is the same as decreasing 40 by one-half of c. So, it is a 50% decrease.
I don't understand how to fill in the blanks.

Answer 1

The first blank is 20 and the second is actually 40

Explanation:

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Answer 2

I believe the answer you are looking for is:

Increasing 20 to 40 is the same as increasing 20 by 20 (or itself), so it is a 100% increase. Decreasing 40 to 20 is the same as decreasing 40 by 1/2 or by 20. So it is a 50% increase.

Basically, when going from 20 to 40, the number is being doubled, and when youre going from 40 to 20 you are cutting the number in half.