A man runs a distance of 9km at a constant speed for the first…
A man runs a distance of 9km at a constant speed for the first 4km and then 2km/hr faster for the rest of the distance. The whole run takes him 1 hour. His average speed for the first 4km is
Total distance = 9km
Speed for the rest of the distance (which is 5km) = X + 2
But recall that distance = speed × time
Total distance = total average speed × total time
Total distance = (X + 1) × 1 = 9
So, X + 1 = 9
X = 9 – 1 = 8km/hr
Now for the right answer to the above question:
- Option A is incorrect.
- Option B is incorrect.
- C is correct.
- D is not the correct answer.
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- There’s another method for resolving this, but we did not feature it here because it lead to simultaneous equations which are somehow longer to solve.
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/ culled from 2020 JAMB-UTME mathematics past question 01 /