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A mixture of 50 kg of cement and gravel contains 10% of gravel. How many kg of gravel must be added to make the gravel content 28% in the new mixture?

A mixture of 50 kg of cement and gravel contains 10% of gravel. How many kg of gravel must be added to make the gravel content 28% in the new mixture? Correct Answer 12.5

Quantity of gravel in 50 kg mixture = 50 × 10/100 = 5kg

Let the quantity of gravel which added be = x kg

According to the question

⇒ (5 + x) / (50 + x) = 28%

⇒ (5 + x) / (50 + x) = 28/100

⇒ (5 + x) / (50 + x) = 7/25

⇒ x = 12.5

∴ 12.5 kg of gravel must be added to make the gravel content 28% in the new mixture.

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