Multiple choice

A mixture of 40 litres of spirit and water contain 10% water. How much water must be added to this mixture to raise the percentage of water to 25%? 40 लीटर स्प्रिट तथा पानी के मिश्रण में 10% पानी है। इसमें कितना पानी और मिलाया जाए कि पानी की मात्रा 25% हो जाये।

  1. 48 litres/लीटर

  2. 24 litres/लीटर

  3. 8 litres/लीटर

  4. 10 litres/लीटर
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In 40 litres mixture, spirit = 36 litres (90%), water = 4 litres (10%). Let x litres water be added. New water percentage = (4 + x)/(40 + x) = 25/100 = 1/4. Cross-multiplying: 4(4 + x) = 40 + x, so 16 + 4x = 40 + x, therefore 3x = 24 and x = 8 litres. Options A (48L) and B (24L) are much too large for this mixture.

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