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The car has changed its speed during its travel.

Otherwise, if it takes 1/2 hrs to travel 2/7 of journey,

it will take 1/4 hr to travel 1/7 of journey (divide by 2);  or

5/4 hr to travel the remaining 5/7 of journey (times 5).

But the car took 3 hrs to travel the remaining 5/7 of journey.

Average speed = Total distance/Total time

Given that the van kept its speed constant at 70km/h, in that last 3 hr, it travelled 70×3=210km.

Car has reached Town Q and distance it travelled is 210+65 = 275km –> 5/7 of journey

                                                                                                                 55km <– 1/7 of journey

                                                                                                              385km <– 7/7 of journey

Average speed = Total distance/Total time =  385 / (0.5+3) = 110km/h#

0 Replies 2 Likes ✔Accepted Answer

70 x 3 = 210
210 + 65 = 275
1 – (2/7) = 5/7 ——- 275
1/7 ——- 275/5 = 55
7/7 ——- 55 x 7 = 385
1/2 + 3 = 3.5 ( total time taken by car to complete the whole journey)
385/3.5 = 110

Ans : 110 km/h.

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