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Pehal and ishaan were making 100g sugar solutions with concentration by mass 20% and 50% respectively. Pehal added 20g of sugar in her solution whereas Ishaan evaporated 20g of water from his solution . Now the two solutions were mixed to form a final solution. The concentration by mass of final solution is

a) 28%

b)45%

c)40%

d)60%

(Answer with solution) plz

20% by mass sugar solution means 20 gm of the sugar is dissolved in 100 gm of solution or 80 gm of water.

50% by mass sugar solution means 50 gm of the sugar is dissolved in 100 gm of solution or 50 gm of water.

Total mass of sugar after mixing = 20gm + 50 gm = 70 gm

Total mass of water after mixing = 80gm + (50-20)gm

= 110 gm

Total mass of solution = 70+110 = 180 gm

The concentration by mass of final solution is: 70gm/180gm * 100

= 39%

The answer is (c) 40 %.

Regards

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