One morning, Justin drove 3 hours before stopping to eat lunch. After lunch, he increased his speed by 10 mph. If he completed a 390-mile trip in 6 hours of driving time, how fast (in miles per hour) did he drive in the morning?

Question

boholmission · Answer

Speed time formula
speed * time = Distance

speed = x
time1 = 3 hours before lunch
time2 = 3 hours after lunch
Distance = 390

(time1*3)+(time2*3)=Distance

Before lunch speed = x for 3 hours = 3x
after lunch speed = x + 10 for 3 hours = 3(x+10)
This totals the 6 hours

3x + 3(x+10) = 390
3x + 3x + 30 = 390
6x = 360
x = 60
In the morning he drove 60 MPH

check answer
In the morning he drove 60 mph for 3 hours totaling 180 miles
in the afternoon he drove 70 mph for 3 hours totaling 210 miles
180+210 = 390 miles for the whole trip
Correct