A runner is running at a speed of 40 kim/h. If he runs at a speed of 30 km/h, then what will the decrease in the percentage of his speed be?

15% 20% 25% 30%

25%

Ratio of initial to New speed =  4  :  3 Decrease in percentage in speed = \(\frac{4 - 3 }{4}\) = 25%