SOLUTION: In January of a certain year, Will deposited $120 in his savings account. For each subsequent month of the same year and each month of the following year, his monthly deposit incre
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Question 1140667: In January of a certain year, Will deposited $120 in his savings account. For each subsequent month of the same year and each month of the following year, his monthly deposit increased by $5. How much did he deposit in the savings account altogether during the two years? Answer by ikleyn(52786) (Show Source):
It is arithmetic progression.
The first term is = 120.
The last, 24-th term is = 120 + 5*(24-1) = 235 dollars.
The amount under the question is the sum of the 24 terms of this progression.
It is equal half the sum = = 177.5, multiplied by the number of terms, i.e. 24:
sum = 177.5*24 = 4260 dollars. ANSWER
