14 bags of fertilizer are needed
Solution:
Given that You need to buy fertilizer for a circular flower bed with a diameter
of 13 feet
Diameter = 13 feet


Therefore radius of circular flower bed is 6.5 feet
Area of circle is given as:

Substitute r = 6.5

Given that one bag will fertilize 10 square feet
1 bag = 10 square feet
Then number of bags needed are:

Thus approximately 14 bags of fertilizer are needed