Question

Pehal and Ishaan were making $100g$ sugar solution 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 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 1

Answer: (B)

$45\%$

For Pehal:- a mass of sugar= $20g$

mass of water=$80g$

The new mass of sugar=$20+20=40g$

$\therefore$Concentration of sugar= $\frac{40}{120}\times 100=33.33$%

For Ishaan:- mass of sugar= mass of water= $50g$

New mass of water= $50-20=30g$

$\therefore$ Concentration of sugar= $\frac{50}{80}\times 100=62.5$%

Concentration by mass of final solution= $\frac{NewmassofsugarinPehal+MassofsugarinIshaan}{NewmassofsolutioninPehal+NewmassofsolutioninIshaan}$

=$\frac{40+50}{120+80}$

=$45$%