Multiple choice

A man purchases a variety of salt at Rs. 21 per kg and mixes it with 25 kg of another variety of salt at Rs. 12 per kg. If he gains 25% on selling the mixture at Rs. 20 per kg, then what was the quantity of salt that he purchased at Rs. 21 per kg?

  1. 15 kg

  2. 18 kg

  3. 20 kg

  4. 23 kg

  5. 25 kg
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let x be the quantity of the first salt. Cost price = 21x + 12*25. Selling price = 20(x+25). Profit 25% means SP = 1.25 * CP. 20(x+25) = 1.25 * (21x + 300). 20x + 500 = 26.25x + 375. 125 = 6.25x. x = 125 / 6.25 = 20 kg.

AI explanation

Selling the mixture at 20 rupees per kg with a 25 percent gain means the cost price per kg is 20 divided by 1.25, which is 16 rupees. Using the method of alligation, the ratio of the 21 rupee salt to the 12 rupee salt is (16 minus 12) to (21 minus 16), which is 4 to 5. Since 5 parts equals 25 kg, 4 parts equals 20 kg, the quantity of salt purchased at 21 rupees per kg.

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