One morning, John drove 6 hours before stopping to eat.After lunch, he increased his speed by 10 mph. If he completed a 390-mile trip in 9 hours of driving time, how fast did he drive in the morning?
A) $\quad 36 \mathrm { mph }$
B) $\quad 40 \mathrm { mph }$
C) $\quad 48 \mathrm { mph }$
D) $\quad 33 \mathrm { mph }$
E) $\quad 43 \mathrm { mph }$

Question

One morning, John drove 6 hours before stopping to eat.After lunch, he increased his speed by 10 mph. If he completed a 390-mile trip in 9 hours of driving time, how fast did he drive in the morning? 
A) $\quad 36 \mathrm { mph }$
B) $\quad 40 \mathrm { mph }$
C) $\quad 48 \mathrm { mph }$
D) $\quad 33 \mathrm { mph }$
E) $\quad 43 \mathrm { mph }$

Quizplus · Accepted Answer

John drove for 6 hours in the morning and 3 hours after lunch for a total of 9 hours. Let $x$ be his speed in the morning. After lunch, his speed was $x + 10$ mph. The total distance is given by the sum of the distances he traveled before and after lunch: $6x + 3(x + 10) = 390$. Solving this equation for $x$ gives $x = 40$ mph.

One Morning, John Drove 6 Hours Before Stopping to Eat 36mph\quad 36 \mathrm { mph }36mph

One Morning, John Drove 6 Hours Before Stopping to Eat $\quad 36 \mathrm { mph }$