SOLUTION: Seventy two grams of fertilizer is given to a dogwood tree the first year, 60 grams the second year, 50 grams the third year, and so on. Find the total amount of fertilizer receive

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Question 1117074: Seventy two grams of fertilizer is given to a dogwood tree the first year, 60 grams the second year, 50 grams the third year, and so on. Find the total amount of fertilizer received by the dogwood tree.
The answer is 432
I don't know how to do this.
Answer by ikleyn(52787) About Me  (Show Source):
You can put this solution on YOUR website!
.
The sum of the infinite geometric progression with the first term a = 72 and the common ratio r = 60%2F72 = 5%2F6


S = a%2F%281-r%29 = 72%2F%281-5%2F6%29 = 72%2F%28%281%2F6%29%29 = 72*6 = 432.

Solved.