Question : How much percentage should a racer increase speed to reduce the time by 20% to cover a fixed distance?
Option 1: 25%
Option 2: 30%
Option 3: 40%
Option 4: 35%
Correct Answer: 25%
Solution : We know, $\text{Speed}=\frac{\text{Distance}}{{\text{Time}}}$ $\text{Speed}\propto\frac{\text{1}}{{\text{Time}}}$ If the distance remains constant, then speed is inversely proportional to time. If the time is reduced by 20%, the new time is 80% (or 0.8 times) of the original time. Since speed is inversely proportional to time, the new speed must be ($\frac{1}{0.8}$) = 1.25 times the original speed to maintain the same distance. An increase from 1 to 1.25 is an increase of 0.25, or 25% when expressed as a percentage. Hence, the correct answer is 25%.
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Question : A man covers a certain distance by bike. If he covers 25% of the distance at the speed of 25 km/hr, 50% of the distance at the speed of 50 km/hr and the remaining distance at the speed of 12.5 km/hr, find his average speed over the whole journey.
Question : The salary of Ramesh first increases by 35%, then decreases by 40%, then again increases by 25%. Find the overall increase or decrease percentage.
Question : A number is first increased by 40% and then decreased by 25%, again increased by 15% and then decreased by 20%. What is the net increase/decrease percentage in the number?
Question : The speed of a boat in still water is 20 km/hr, while the river is flowing at a speed of 8 km/hr and the time taken to cover a certain distance upstream is 6 hr more than the time taken to cover the same distance downstream. Find the distance.
Question : If A earns 25% more than B then how much percentage does B earn less than A:
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