In the \( 1980 \mathrm{~s} \), the population of Pleasanton decreased by \( 10 \% \). In the \( 1990 \mathrm{~s} \), its population increased by \( 20 \% \). How does the population of Pleasanton at the end of the 1990 s compare with its population in 1980 ?
It is \( 12 \% \) higher.
It is \( 8 \% \) higher.
It is \( 10 \% \) higher.
It is \( 30 \% \) higher.

Answer

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Answer

Percentage increase at end of 1990s: \(\frac{1.08x - x}{x}\times 100 = 8\%\).

Steps

Step 1 ：Let Pleasanton's initial population in 1980 be \(x\).

Step 2 ：Population decreased by \(10\%\) in 1980s: \(0.9x\).

Step 3 ：Population increased by \(20\%\) in 1990s: \((1+0.2)(0.9x) = 1.08x\).

Step 4 ：Percentage increase at end of 1990s: \(\frac{1.08x - x}{x}\times 100 = 8\%\).