speed time distance CAR r+p t D TRUCK r t d
Let auto's speed be S
Then truck's speed is: S - 15
Time auto takes to travel 200 km:
Time truck takes to travel 150 km:
Since times are the same, we get:
200(S - 15) = 150S ----- Cross-multiplying
200S - 3,000 = 150S
200S - 150S - 3,000
50S = 3,000
S, or auto's speed =, or km/h