The train speed has increased from 75 km / h to 80 km / h. By what percentage will the time spent

The train speed has increased from 75 km / h to 80 km / h. By what percentage will the time spent by the train on the same path decrease?

Time t = S / V, where S is the path and V is the speed. By condition, the path is the same.
Time difference in%: Δt = (((S / 75) – (S / 80)) * 100%) / (S / 75);

Let’s represent the speed in the form of factors:

(75 = 5 * 15; 80 = 5 * 16) = (((S / (5 * 15) – (S / (5 * 16)) 100 / (S / (5 * 15));

Let us bring the expressions for the time in the numerator to a common denominator and subtract the fractions:

(((S * 16 – S * 15) / (5 * 15 * 16)) * 100) / (S / (5 * 15) = ((S / (5 * 15 * 16) * 100) / S / (5 * 15);

Divide the numerator and denominator by S / (5 * 15), reduce 100/16 = 6.25%.
Answer: 6.25%.