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Question
A bicycle wheel, diameter 56 cm, is making 45 revolutions in every 10 seconds. At what speed in kilometre per hour is the bicycle traveling?
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Solution
Diameter = 56 cm
∴ Radius, r = 28 cm
∴ Distance travelled in 1 revolution
i.e. circumference = `2pir = 2 xx 22/7 xx 28 = 176` cm
∴ Distance travelled in 45 revolution
= `176 xx 45 = 7920 "cm" = 7920/(100 xx 1000)`km
Time = 10 sec = `10/(60 xx 60)` hr.
Speed = `(7920/(100 xx 1000))/(10/(60 xx 60))`m
= `7920/(100 xx 1000) xx (60 xx 60)/10 = 28512/1000` km/hr
= 28.512 km/hr
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