CAT Practice : Percents, Profits

Combining simple ideas from two topics is a very interesting method to create new questions.

Profit - Progressions

    Q.1: A merchant can buy goods at the rate of Rs. 20 per good. The particular good is part of an overall collection and the value is linked to the number of items that are already on the market. So, the merchant sells the first good for Rs. 2, second one for Rs. 4, third for Rs. 6…and so on. If he wants to make an overall profit of at least 40%, what is the minimum number of goods he should sell?
    1. 24
    2. 18
    3. 27
    4. 32

 

  • Correct Answer
    Choice C. 27

Detailed Solution

Let us assume he buys n goods.
Total CP = 20n
Total SP = 2 + 4 + 6 + 8 ….n terms
Total SP should be at least 40% more than total CP
2 + 4 + 6 + 8 ….n terms ≥ 1.4 * 20 n
2 (1 + 2 + 3 + ….n terms) ≥ 28n
n(n + 1) ≥ 28n
n2 + n ≥ 28n
n2 - 27n ≥ 0
n ≥ 27
He should sell a minimum of 27 goods.
Answer Choice (C)

Correct Answer: 27



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