7+10.5+14+...+84 find the sum of ap
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d=3.5 an=84 a=7
sn=n/2 [2a+(n-1)d]
s7=7/2 [2×7+6×3.5]
=7/2 [14+9.5]
=7/2[23.5]
=3.5×23.5
=82.25
there for sum us equal to 82.25
sn=n/2 [2a+(n-1)d]
s7=7/2 [2×7+6×3.5]
=7/2 [14+9.5]
=7/2[23.5]
=3.5×23.5
=82.25
there for sum us equal to 82.25
dastagiramanullah:
I think this the correct answer for the question
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