Question

For each of the following situations, is the percent of change between 20% and 30%?

a) A $12 cost increases to $15
b) A boys height increases from 52 inches to 61 inches
c) The temperature falls from 3 degrees to 2 degrees.

Answer 1

a) yes

b) no

c) no

Explanation:

a) The percentage change from 12 to 15 is ...

(15/12 -1)·100% = 1/4·100% = 25% . . . . between 20% and 30%

__

b) The height increased by 61-52 = 9 inches. 20% of 52 inches is 10.4 inches, so the increase was less than 20%.

__

c) The increase was negative, so was not between two positive values.

___

In summary ...

a) yes, 25% is between 20% and 30%

b) no, 17.3% is NOT between 20% and 30%

c) no, -33.3% is NOT between 20% and 30%

_____

A percentage change can be calculated from ...

((new value)/(old value) -1) × 100%