Discussion

Explanation:

If he travels at minimum speed over stretch A (i.e. 40 km/hr), the total time taken to cover this stretch $=\left(\frac{2}{40}\right)=\frac{1}{20}$ hr = 3 min.

If he then travels at the fastest speed over stretch B (i.e. 50 km/hr), the total time taken to cover this stretch = $\left(\frac{2}{50}\right)=\frac{1}{25}$ = 2.4 min.

Thus, total time taken over the first two stretches = (3 + 2.4) = 5.4 min.
In order to break the previous record he will have to cover the third stretch in (10 – 5.4) = 4.6 min. To do this he will have to cover the third stretch at $\left(\frac{2}{4.6}\right)$ = 0.434 km per minute or 26.08 km/hr. But the maximum speed over the stretch C is 20 km/hr. Hence, it is not possible for C to break the previous record.

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