Question

If the cost of bananas is increased by ₹ 2, then one can get one dozen less bananas for ₹840. Find the original cost of one dozen of bananas​

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Answer 1

Let the cost of bananas per dozen be x

According to given condition,

840/x – 840 / x + 1 = 2

∴ 840[1/x – 1/x+1] = 2

∴ 840 [x+1- x / x(x+1)] = 2

∴ 840 [1/ (x2 + x)] = 2

∴ 840 = 2(x2 + x)

∴ 2x2 + 2x – 840 = 0

Dividing by 2, we get

x2 + x – 420 = 0

x2 – 20x + 21x – 420 = 0

∴ x (x – 20) + 21 (x – 20) = 0

∴ x – 20 = 0 or x + 21 = 0

∴ x = 20 or x = –21

∴ The cost of bananas cannot be negative.

∴ x = 20

The original cost of one dozen banana is Rs. 20

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