Raju can travel from his house to school in x hours if he does not stop anywhere One day he increase...........

Quant (SSC) Time & distance

Raju can travel from his house to school in x hours if he does not stop anywhere. One day, he increases his speed by 4 km per hour but stops for 15 minutes on a tea shop then he reaches 5 minutes earlier. If the distance from his house to the school is 40 km then find the value of x?

1.7

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Explanation:

Let the speed = a km per hr
When he increases his speed by 4 km per hour
New speed = a + 4 km per hour
He stops for 15 minutes on a tea shop then he reaches 5 minutes earlier it means if he had not stopped for 15 minutes then he would have reached 15 + 5 = 20 minutes earlier @ a + 4 km per hour
We know that, time = distance/time
40/a - 40/a + 4/a + 4 = 20/60
40 × 3(a + 4 – a) = a (a + 4)
40 × 3 × 4 = 480 = a (a + 4)
By solving, a = 20 km per hour
Value of x = ditance/speed = 40/20 = 2 hrs