Question

A car covers 20 km in 1 hr., 30 km in 2 hrs. and 40 km in 3 hrs.The average speed of car
is 5x km/hr find x.​

Answer 1

Yo yo

Formula: Speed = Distance/ Time, Therefore, Time = Distance / speed

Given that speed of the car is 20km/hr more than the average speed of the bus, Let the speed of the bus be x,

Therefore speed of the car is x+20.

Average speed of the bus:

300/x - 4=300/x+20

=> 300[x+20-x/x(x+20)]= 4

=> 300(20/ x(x+20)) = 4

=> 300(20/x²+20x) = 4 (upon cross multiplying)

=> 6000= 4x²+80x

4x²+80x-6000=0

4(x² + 20x -1500) =0

x²+20x-1500=0

Upon factorizing,

(x+50)(x-30)=0

x=30

The bus goes 30 kmph; the car goes 50 kmph