Kamal

Kamal walks to his school which is at a distance of 3 km from his home in 30 minutes. On reaching he finds that the school is closed and comes back by a bicycle with his friend and reaches home in 20 minutes. His average speed in km/h is

Correct answer:

v =  7.2 km/h

Step-by-step explanation:

$$\begin{gathered} s=3\text{km} \\ {t}_1=30\text{min}\to \text{h}=30:60\text{h}=0.5\text{h} \\ {t}_2=20\text{min}\to \text{h}=20:60\text{h}=0.33333\text{h} \\ v=\frac{2\cdot s}{t_1+t_2}=\frac{2\cdot 3}{0.5+0.3333}=\frac{36}{5}\text{km/h}=7.2\text{km/h} \end{gathered}$$

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