Kamal

Kamal walks to his school, which is 3 km from his home, in 30 minutes. On reaching, he finds that the school is closed and comes back by 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:

$$\begin{gathered} s=3\text{km} \\ {t}_1=30\text{min}\to \text{h}=30:60\text{h}=0.5\text{h} \\ {t}_2=20\text{min}\to \text{h}=20:60\text{h}=0.33333\text{h} \\ v=\frac{2\cdot s}{t_1+t_2}=\frac{2\cdot 3}{\frac{1}{2}+\frac{1}{3}}=\frac{36}{5}\text{km/h}=7.2\text{km/h} \end{gathered}$$

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