Question

Raghubir after travelling 84 km, found that if he traveled at 5 km an hour more,
he would have taken 5 hrs less, he actually travelled at a rate of: *
05 km/hour
O 6 km/hour
O 7 km/hour
8 km/hour
O
10 km/hour​

Answer 1

Answer:

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Step-by-step explanation:

Distance Raghubir travelled = 84 km

Let his original speed be s km/hr and original time be t hrs

s t = 84....(1)

Now, his speed is = s + 5

and time = t - 5

So,

(s + 5) (t - 5) = 84

st - 5s + 5t - 25 = 84....(2)

From, (1) we have,

t = 84/s

Putting this in (2), we get

s(84/s) - 5s + 5(84/s) - 25 = 84

84 - 5s + 420/s - 25 = 84

420/s - 5s -25 = 0

420 - 5s² - 25s = 0

s² + 5s - 84 = 0

s² + 12s - 7s - 84 = 0

s(s + 12) - 7(s + 12) = 0

(s + 12)(s - 7) = 0

s = 7 or -12

But speed cant be negative, so s = 7

Therefore, speed of Raghubir is 7 km/hr.