From 7:45 p.m. to 9:30 p.m., Jim drove a distance of $84 \mathrm{~km}$ at a constant speed. What was this speed, in $\mathrm{km} / \mathrm{h}$ ?
(A) 60
(B) 80
(C) 112
(D) 63
(E) 48
Solution 1

Since Jim drives from 7:45 p.m. to 9:30 p.m., then Jim drives for 1 hour and 45 minutes or $1 \frac{3}{4}$ hours or $\frac{7}{4}$ hours.

Since Jim drives $84 \mathrm{~km}$ in $\frac{7}{4}$ hours at a constant speed, then this speed is $\frac{84}{\frac{7}{4}}=84 \times \frac{4}{7}=48 \mathrm{~km} / \mathrm{h}$.

## Solution 2

Since Jim drives from 7:45 p.m. to 9:30 p.m., then Jim drives for 1 hour and 45 minutes, which is the same as 7 quarters of an hour.

Since he drives $84 \mathrm{~km}$ in 7 quarters of an hour, he drives $12 \mathrm{~km}$ in 1 quarter of an hour, or $48 \mathrm{~km}$ in one hour, so his speed is $48 \mathrm{~km} / \mathrm{h}$.

ANSWER: (E)