SOLUTION: The sum of first 3 integers in an Arithmetic progression is 36. The sum of the next 3 integers is 72. What is the common difference between the terms?

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Question 847267: The sum of first 3 integers in an Arithmetic progression is 36. The sum of the next 3 integers is 72. What is the common difference between the terms?
Answer by stanbon(75887) About Me  (Show Source):
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The sum of first 3 integers in an Arithmetic progression is 36. The sum of the next 3 integers is 72. What is the common difference between the terms?
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S(3) = (3/2)(a + (a+2d)) = 36
S(6) = (6/2)(a + (a+5d)) = 72+36
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Rearrange:
3(2a+2d) = 72
6(2a+5d) = 216
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2a+2d = 24
2a+5d = 36
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3d = 12
common difference = 4
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Cheers,
Stan H.
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