You have a box that contains 200 marbles. 99% of the marbles are green, the other 1% are white.

Question

How many green marbles would you have to remove from the box to reduce the percentage of green marbles to 98%?

Answer 1

Green = 0.99*200 = 198

White = 0.01*200 = 2

X green marbles removed.
(200-x) Marbles remaining.

0.98(200-x) + 2 = 200-x
196-.98x + 2 = 200-x
0.02x = 200-198 = 2
X = 100 Green marbles removed.

198-100 = 98 Green marbles remaining.
200-100 = 100 total Marbles remaining.

Check:
Green/Total = 98/100 = 0.98 = 98% Green
marbles remaining.