Question 54

A man travels 75 km at a speed 25 km/h and the next 60 km at 20 km/h and thereafter travels 90 km at 15 km/h. His average speed is:

Solution

A man travels 75 km at a speed 25 km/h and the next 60 km at 20 km/h and thereafter travels 90 km at 15 km/h.

$$Average\ speed=\frac{total\ distance}{total\ time}$$

$$=\frac{75+60+90}{\frac{75}{25}+\frac{60}{20}+\frac{90}{15}}$$

$$=\frac{225}{3+3+6}$$

$$=\frac{225}{12}$$

= 18.75 km/h

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