If \(p\) is a price in whole cents, which of the following could NOT be the result of increasing \(p\) by \(20\%?\)

[Gmat_mission]

If \(p\) is a price in whole cents, which of the following could NOT be the result of increasing \(p\) by \(20\%?\)

A. \(\$1.20\)
B. \(\$1.25\)
C. \(\$1.38\)
D. \(\$1.80\)
E. \(\$2.52\)

Answer: B

Source: Princeton Review

[Scott@TargetTestPrep]

If \(p\) is a price in whole cents, which of the following could NOT be the result of increasing \(p\) by \(20\%?\)

A. \(\$1.20\)
B. \(\$1.25\)
C. \(\$1.38\)
D. \(\$1.80\)
E. \(\$2.52\)

Answer: B

Solution:

Notice that $1.25, or 125 cents, is the only odd number of cents of the answer choices, so we will guess that $1.25 couldn’t be the result of increasing p by 20%. In other words, if p is increased by 20% and the result is $1.25, p couldn’t be a whole number of cents. Let’s show that this is indeed the case.

p x 1.2 = 125

p = 104.167

We see that 104.167 is not a whole number.

Answer: B