Find the sum of the terms from

Lisa Cooper

Lisa Cooper

Answered question

2022-04-06

Find the sum of the terms from a16  a23​ inclusive. Use the sum formula for arithmetic sequences.
7,10,13,16,

Answer & Explanation

awalkbyfaithbzu6

awalkbyfaithbzu6

Beginner2022-04-07Added 21 answers

Given 7,10,13,16,
First term a=7
Common difference d=207=3
We need to find the sum of terms from a16 to a23
Sum of n terms:
Sn=n2(2a+(n1)d)
Sum of first 15 terms
S15=152(2(7)+(151)(3))
=152[14+14(3)]
=152[56]
=420
Sum of first 23 terms
S23=232(2(7)+(231)(3))
=232[14+66]
=920
The sum of terms from a16 to a23
=S23S15
=920420
=500

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