Question

If a car had increased its average speed for a 210 km journey by 5 kmph, the journey
would have been completed in one hour less. What was the original speed of the car
for the journey?
(1) 28 kmph
(2) 32 kmph
(3) 30 kmph
(4) 35 kmph​

Answer 1

Answer:

a car had increased its average speed for a 210 mile journey by 5 MPH the journey would have been completed in one hour less.

What was the original speed of the car for the journey?

:

Let s = original speed

then

(s+5) = the faster speed

:

Write a time equation; time = dist/speed

:

original time - faster time = 1 hr

210%2Fs - 210%2F%28%28s%2B5%29%29 = 1

multiply equation by s(s+5); results:

210(s+5) - 210s = 1s(s+5)

:

210s + 1050 - 210s = s^2 + 5s

Arrange as a quadratic equation

s^2 + 5s - 1050 = 0

You can use the quadratic equation, but this will factor

(s-30)(s+35) = 0

the positive solution is all we want here

s = 30 mph is the original speed

so your answer is 30kmph

Hope it is helpful for you