Question 70

A student takes 1.25 hours to travel from home to school at a speed of 4 km/h. By what percentage should he increase his speed to reduce the time by 25% to cover the same distance from school to home?

Solution

Distance = time $$\times$$ speed = 1.25 \times 4 = 5 km$$

Time reduce by 25% so time = 1.25 $$\times 75/100 = 0.9375

Speed = distance/time = 5/0.9375 = 5.33

Increment in speed = 5.33 - 4 = 1.33

Percentage increment = $$\frac{1.33}{4} \times 100 = 33\frac{1}{3}

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