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(B) Let the speed of car $P$ be $u \, km/hr$ and the speed of car $Q$ be $v \, km/hr$.When the cars travel in opposite directions,their relative speed

Vedclass · Accepted Answer

$70$

Vedclass · Answer

(B) Let the speed of car $P$ be $u \, km/hr$ and the speed of car $Q$ be $v \, km/hr$.When the cars travel in opposite directions,their relative speed is $(u + v)$.Since they meet after $1 \, hour$ over a distance of $120 \, km$,we have: $u + v = \frac{120}{1} = 120 \dots (1)$.When the cars travel in the same direction,their relative speed is $(u - v)$.Since they meet after $6 \, hours$ over a distance of $120 \, km$,we have: $u - v = \frac{120}{6} = 20 \dots (2)$.Adding equation $(1)$ and $(2)$,we get: $(u + v) + (u - v) = 120 + 20$.$2u = 140$,which implies $u = 70 \, km/hr$.Thus,the speed of car $P$ is $70 \, km/hr$.

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