arithmetic
posted by Anonymous .
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.

21terms/3terms=7groups of 3terms
237(last group)129 (middle group)=36
237(group7)36=201(group6)
group636
group536
129(group4)36=95(group3)
group336
group236
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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