**Q) In a chemistry lab, there is some quantity of 50% acid solution and some quantity of 25% acid solution. How much of each should be mixed to make 10 litres of 40% acid solution?**

**Ans: **Let consider quantity of 50% acid solution be V litres

∵ total quantity of final solution is 10 litres

∴ quantity of 25% acid solution will be: (10 – V) litres

Amount of acid should balance out in mix of solution with that in final solution

∴ V x 50% + (10 – V) x 25% = 10 x 40%

0.5 V + 2.5 – 0.25 V = 4.0

0.25 V + 2.5 = 4.0

0.25 V = 4.0 – 2.5 = 1.5

V = = 6

∴ (10 – V) = 10 – 6 = 4

**Therefore, quantity of 50% acid solution is 6 litres and 25% acid solution is 4 litres in the final 10 litres of 40% acid solution.**

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