The formula for calculating the percent change in a value between two points in time is:
p = (N - O)/O * 100p=N−OO⋅100
Where:
pp is the percent change - -28% for this problem.
NN is the New Value - 18 in this problem.
OO is the Old Value - what we are solving for in this problem.
Substituting and solving for OO gives:
-28 = (18 - O)/O * 100−28=18−OO⋅100
-28 = (18/O - O /O) * 100−28=(18O−OO)⋅100
-28 = (18/O - 1) * 100−28=(18O−1)⋅100
-28 = (18/O * 100) - (1 * 100)−28=(18O⋅100)−(1⋅100)
-28 = 1800/O - 100−28=1800O−100
-28 + color(red)(100) = 1800/O - 100 + color(red)(100)−28+100=1800O−100+100
72 = 1800/O - 072=1800O−0
72 = 1800/O72=1800O
color(red)(O)/color(blue)(72) xx 72 = color(red)(O)/color(blue)(72) xx 1800/OO72×72=O72×1800O
color(red)(O)/cancel(color(blue)(72)) xx color(blue)(cancel(color(black)(72))) = cancel(color(red)(O))/color(blue)(72) xx 1800/color(red)(cancel(color(black)(O)))
O = 1800/color(blue)(72)
O = 25
Last year there were color(red)(25) 8th grade Teams
