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1. A motor car does a journey in 17.5 hours, covering the first half at 30 km/h and the second half at 40 km/h. Find the distance of the journey?

A. 684 km

B. 600 km

C. 624 km

D. 584 km

Solution:

Let the total distance be 2X.

A_____X km_____M_____X km_____B

Total time taken in the journey = 17.5 hours
Time taken to cover X km at 30 km/h =

\frac{X}{30}

Time taken to cover X km at 40 km/h =

\frac{X}{40}

Now,

\begin{aligned} \frac{X}{30} + \frac{X}{40} = 17.5 \\ \frac{40 X + 30 X}{1200} = 17.5 \\ 70 X = 17.5 \times 1200 \\ X = 300 k m \\ Total distance, 2 x \\ = 600 k m \end{aligned}

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