SOLUTION: The arithmetic progression consists of 15 terms. If the sum of the 3 terms
in the middle is 27 and the sum of the last 3 terms is 18, then what is the
sum of the first 3 terms?
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-> SOLUTION: The arithmetic progression consists of 15 terms. If the sum of the 3 terms
in the middle is 27 and the sum of the last 3 terms is 18, then what is the
sum of the first 3 terms?
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Question 1083553: The arithmetic progression consists of 15 terms. If the sum of the 3 terms
in the middle is 27 and the sum of the last 3 terms is 18, then what is the
sum of the first 3 terms? Answer by ikleyn(52788) (Show Source):
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The arithmetic progression consists of 15 terms. If the sum of the 3 terms
in the middle is 27 and the sum
of the last 3 terms is 18, then what is the sum of the first 3 terms?
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"If the sum of the 3 terms in the middle is 27" then = = 9 (why ?)
Also, "if the sum of the last 3 terms is 18" then = = 6.
Thus you have
= = 9 (1) and
= = 6 (2)
It implies that 6d = 6 - 9 = -3. Hence, d = = -0.5.
Then = = 9 - 6*(-0.5) = 9 + 3 = 12.
Hence, the sum = 36 (why ?)
