Chris and Pat go on a $30 \mathrm{~km}$ run. They both usually run at $10 \mathrm{~km} / \mathrm{h}$. If Chris runs at $\frac{1}{2}$ his usual running speed, and Pat runs at $1 \frac{1}{2}$ times her usual speed, how many more hours does it take Chris to complete the run than it takes Pat to complete the run?
(A) 1
(B) 1.5
(C) 2
(D) 4
(E) 6
Since Chris runs $\frac{1}{2}$ as fast as his usual running speed, he runs at $5 \mathrm{~km} / \mathrm{h}$, and so will take 6 hours to complete the $30 \mathrm{~km}$ run.

Since Pat runs at $1 \frac{1}{2}$ her usual running speed, she runs at $15 \mathrm{~km} / \mathrm{h}$, and so will take 2 hours to complete the $30 \mathrm{~km}$ run.

Thus, it takes Chris 4 hours longer to complete the run than it takes Pat.

ANsWER: (D)

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