Question 79

Two cars travel from city A to city B at a speed of 30 and 45 km/hr respectively. If one car takes 2.5 hours lesser time than the other car for the journey, then the distance between City A and City B is:

Solution

Let the distance between City A and City B = $$d$$ km

Speed of first car = 30 km/hr and speed of second car = 45 km/hr

Let time taken by first car = $$t$$ hrs and time taken by second car = $$(t - 2.5)$$ hrs

Using, speed = distance/time for first car :

=> $$\frac{d}{t} = 30$$

=> $$d = 30t$$ --------------(i)

For second car, => $$\frac{d}{t - 2.5} = 45$$

Substituting value of $$d$$ from equation (i), we get :

=> $$30t = 45t - 112.5$$

=> $$45t - 30t = 15t = 112.5$$

=> $$t = \frac{112.5}{15} = 7.5$$ hrs

From equation (i), => $$d = 30 \times 7.5 = 225$$ km

=> Ans - (D)


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