A 20 oz smoothie is 15% protein powder by weight. If you want 25% protein powder, how much protein powder should you add?
Answer
2.67 oz
How to solve it
1
Current protein: 20 × 0.15 = 3 oz
2
Let x = oz to add
3
New equation: (3 + x)/(20 + x) = 0.25
4
Solve: 3 + x = 5 + 0.25x
5
0.75x = 2
6
x = 2.67 oz
Hints
Calculate current protein amount
Set up equation for new concentration
Solve for amount to add