Question
A car completed a journey of 400 km in 12$1/2$ hrs. The first $3/4$th of the journey was done at 30 km/hr. Calculate the speed for the rest of the journey.
Answer: Option A
Answer: (a)Total distance covered = 400 km.Total time = $25/2$ hours$3/4$th of total journey= $3/4$ × 400 = 300 km.Time taken = $\text"Distance"/ \text"Speed"$= $300/30$ = 10 hoursRemaining time = $25/2$ –10= ${25 - 20}/2 = 5/2$ hoursRemaining distance = 100 km.∴ Required speed of car= $100/{5/2} = {100 × 2}/5$ = 40 kmph.
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Answer: (a)Total distance covered = 400 km.Total time = $25/2$ hours$3/4$th of total journey= $3/4$ × 400 = 300 km.Time taken = $\text"Distance"/ \text"Speed"$= $300/30$ = 10 hoursRemaining time = $25/2$ –10= ${25 - 20}/2 = 5/2$ hoursRemaining distance = 100 km.∴ Required speed of car= $100/{5/2} = {100 × 2}/5$ = 40 kmph.
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