Sophia buys jellybeans at 5 for 3 cents, and sells them at 6 for 5 cents. How many must she sell in order to make a profit of $3.50?
1 jellybean costs 3/5¢ and sells for 5/6¢.
The profit per jellybean is 5/6¢ – 3/5¢ = (25 – 18)/30¢ = 7/30¢.
Sophia sells x jellybeans for a profit of $3.50 or 350¢.
(7/30)x = 350 → x = (350 · 30)/7 = 1500 jellybeans.