Physics
It takes much longer to cook food in the hills than in the plains, because

due to low atmospheric pressure on the hills, the water boils at a temperature higher than 100oC and therefore water takes longer to boil
n the hills the atmospheric pressure is lower than that in the plains and therefore water boils at a temperature lower than 100oC causing an increase in cooking time
in the hills the humidity is high and therefore a lot of heat is absorbed by the atmosphere leaving very little heat for cooking
in the hills the atmospheric density is low and therefore a lot of heat is lost to the atmosphere

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Physics
It is easier to roll a stone up a sloping road than to lift it vertical upwards because

Work done in rolling is more than in lifting.
Work done in lifting the stone is equal to rolling it.
Work done in both is same but the rate of doing work is less in rolling.
Work done in rolling a stone is less than in lifting it.

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