Question

Two cars leave town at the same time and travel in opposite directions. The average speed of one car is 15 mph faster than the average rate of speed of the other car. The Carrs are 375 miles apart after 3 hours. Find the average speed rate of the two cars.

Guys please help me with this! I've tried 3 times, first was mph >100 which isn't reasonable, and the other times I kept on eliminating the variable all together (like 0 = 330) which I know is incorrect. I think the correct equations are x = y+15 and 3x - 3y = 375 but I'm really confused on this one. Please show me how to solve it .-.

Answer 1

speed of slower car --- x
speed of faster car ---- x + 15

3x + 3(x+15) = 375
6x + 45 = 375
6x = 330
x = 55

so speeds are 55 and 70 mph

check:
slower car went 3(55) or 165 miles
faster care went 3(70) or 210 miles
165 + 210 = 375

Answer 2

Thank you Reiny!!