Question

find sum of 1+3+5+9+13+7.....upto 20 terms​

Answer 1

20(2+19*2)

10(2+38)

400

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Answer 2

This is an A.P. with first term a=1 and common difference,d=2

S20=?

Sn=n(2a+(n-1)d)/2...........(by formula)

S20=20(2×1+(20-1)/2

S20=20(2+19)/2

S20=10×21

S20=210

Hope it helps u ^_^ ^_^ ^_^

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