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A car covers 300 km at 50 km per hour. At 75 km per hour the same trip would take:
A3 hours
B4.5 hours
C5 hours
D4 hours
Answer & Solution
Correct answer: D. 4 hours
1. At 50 km per hour the trip takes 300 / 50 = 6 hours.
2. The distance is unchanged, so speed and time are in inverse proportion.
3. At 75 km per hour the time is 300 / 75.
4. That is 4 hours.
5. As a check, the speed rose by a factor of 1.5 and the time fell by the same factor, 6 / 1.5 = 4.
_Source: NCERT Class 8 Maths, Ch 11 'Direct and Inverse Proportions', S11.3 Inverse Proportion_
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