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In a mixture of 80 litres of petrol and ethanol, 25% of the mixture is petrol. How much ethanol should be added to the mixture so that petrol becomes 20% of the mixture?

In a mixture of 80 litres of petrol and ethanol, 25% of the mixture is petrol. How much ethanol should be added to the mixture so that petrol becomes 20% of the mixture? Correct Answer 20 litres

Given:

Total initial mixture = 80 litres

The percentage of petrol in the mixture is 25%

Calculation:

The quantity of petrol in initial mixture = 25/100 × 80 = 20 litres

The quantity of ethanol in initial mixture = 80 - 20 = 60 litres

The amount of ethanol added be x

According to the question;

⇒ 20/(60 + x) = 20/80

⇒ 80 = 60 + x

⇒ x = 20 litres

∴ The amount of ethanol added is 20 litres

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