Answer:
8 pounds
Explanation:
- Ratio of C:N = 30:1
- C - carbon content, N - nitrogen content
Given
- Coffee grounds = 1 pound contains 25% C and 1% N
- Rotten vegetables = 6 pounds contains 10% C and 1% N
- Dry leaves = ? pound contains 30% C and 0.5% N
Solution
Coffee grounds and Rotten vegetables together give:
- 1 + 6 = 7 pounds
- C = 1*0.25 + 6*0.1 = 0.25 + 0.6 = 0.85
- N = 1*0.01 + 6*0.01 = 0.01 + 0.06 = 0.07
Add dry leaves of x pounds:
- Total = 7 + x
- C = 0.85 + 0.3x
- N = 0.07 + 0.05x
Finding required weight of dry leaves:
- (0.85 + 0.3x)/(0.07+0.005x) = 30/1
- 0.85 + 0.3x = 30(0.07 + 0.005x)
- 0.85 + 0.3x = 2.1 + 0.15x
- 0.3x - 0.15x = 2.1 - 0.85
- 0.15x = 1. 25
- x = 1.25/0.15
- x = 8.33 pounds = 8 pounds rounded to nearest pound