Answer:
6 pounds of fertilizer.
Step-by-step explanation:
We can solve this problem using rule of three:
Anna needs to use 4 pounds of fertilizer for each 120 square feet of soil. With that values, we make the first fraction: 4/120
Now, she needs X pounds of fertilizer for 180 square feet of soil. The fraction now is X/180
Then, we need to make the first fraction equal to the second, and then find the value of X:
4/120 = X/180
X = 4*180/120 = 6
So Anna will need 6 pounds of fertilizer.
Another way to solve this problem is calculating the amount of soil for one pound of fertilizer:
If 4 pounds of fertilizer is necessary for 120 square feet of soil, 1 pound is necessary for 120/4 = 30 square feet of soil.
If we have 180 square feet of soil, we divide 180 by 30 to find the amount of fertilizer necessary:
180/30 = 6 pounds of fertilizer.