During a journey a person travels half of the distance at a speed of 18 km/h and the remaining half of the journey at a speed of 22 km/h. What is his average speed for the entire journey?
average speed for the entire journey =Â $$\frac{2\times\ Speed_1\times\ Speed_2}{Speed_1+Speed_2}$$
= $$\frac{2\times18\times\ 22}{18+22}$$
=Â $$\frac{2\times18\times\ 22}{40}$$
= $$\frac{9\times\ 22}{10}$$
= $$\frac{198}{10}$$
=Â 19.8 km/h
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