CAT 2021 Slot 1 QA Question 12: The strength of an indigo solution in percentage is equal to the amount of indigo in grams per 100 cc of water. Two 800 cc bottles are filled with indigo solutions of strengths 33% and 17%, respective

Question

The strength of an indigo solution in percentage is equal to the amount of indigo in grams per 100 cc of water. Two 800 cc bottles are filled with indigo solutions of strengths 33% and 17%, respective

Accepted Answer

Let $v$ cc of solution be thrown away from the first bottle and replaced by $v$ cc from the second bottle.
The amount of indigo in the first bottle after replacement is
$0.33(800-v) + 0.17v$
The final strength is 21%, so
$0.33(800-v) + 0.17v = 0.21 	imes 800$
$264 - 0.16v = 168$
$v = 600$
So 600 cc