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Question
A person of mass 60 kg wants to lose 5kg by going up and down a 10 m high stairs. Assume he burns twice as much fat while going up than coming down. If 1 kg of fat is burnt on expending 7000 kilo calories, how many times must he go up and down to reduce his weight by 5 kg?
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Solution
Given, the height of the stair = h = 10 m
The energy produced by burning 1 kg of fat = 7000 cal
∴ The energy produced by burning 5 kg of fat = 5 × 7000 = 35000 kcal
35 × 106 cal
The energy utilised in going up and down one time
= `mgh + 1/2 mgh`
= `3/2 mgh`
= `3/2 xx 60 xx 10 xx 10`
= 9000 J
= `9000/4.2`
= `3000/1.4` cal
∴ A number of times, the person has to go up and down the stairs
= `(35 xx 10^6)/(3000/1.4)`
= `(35 xx 1.4 xx 10^6)/3000`
= 16.3 × 103 times
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