Answer: Decrease of 37.5%
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Work Shown
a = old value = 136
b = new value = 85
c = change in values
c = b-a
c = 85-136
c = -51
The negative c value tells us that we have a percent decrease
Divide that over the starting value a = 136
c/a = -51/136 = -0.375
We have a percent decrease of 37.5%
Move the decimal point two spots to the right to go from 0.375 to 37.5%
Or multiply 0.375 with 100% to get 0.375*100% = 37.5%
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Another approach:
a = old value = 136
b = new value = 85
b/a = ratio of new over old
b/a = 85/136 = 0.625
Subtract off 1 to get
0.625 - 1 = -0.375 which then converts to -37.5% to represent a decrease of 37.5%