Answer:
B) 77%; percent of decrease
Explanation:
First, start by using the process of elimination:
From 31 in. to 7 in., it's probably a decrease.
So now you're down to choices:
B) 77%; percent of decrease
and
C) 23%; percent of decrease.
Now, you can use a ratio:
31 in 100%
------- = ----------
7 in x%
Then, cross multiply:
31x = 7 (100)
31x = 700
x = 22.58064...
x ≈ 22.58%
So 7 in. is about 23% of 31 in. To find the difference between 31 in. and 7 in., subtract the amounts to find the change between them:
100% – 22.58...% = x% of change
≈ 77.4% of change