# arithmetic

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an ap consists of 21 terms.the sum of 3terms in the middle is 129 and of the last three is 237 find the AP.

• arithmetic -

21terms/3terms=7groups of 3terms

237(last group)-129 (middle group)=36

237(group7)-36=201(group6)
group6-36
group5-36
129(group4)-36=95(group3)
group3-36
group2-36
add up all group terms(237+201+165...)

Hope that's what your looking for if not sorry, but that should be right

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