A mixture contains 15% of substance A and 85% of substance B. If you add more of A so that the new mixture contains 35% A, by what percentage did A increase?
Show answer & explanation
Correct answer: B
Explanation
Given:
Initial A = 15%, B = 85%
New A = 35%
Let us assume the total mixture = 100 units.
Initial A = 15 units.
Let 'x' units of A be added.
New A = 15 + x
Total mixture = 100 + x
(15 + x) / (100 + x) = 35/100
100(15 + x) = 35(100 + x)
1500 + 100x = 3500 + 35x
65x = 2000
x = 2000/65
Percentage increase = (x / 15) × 100
= (2000/65 ÷ 15) × 100 = 205.13%