Question

The sum of the first and 17th term of an arithmetic sequence is 40.The sum of first and 18th term is 43
A) what is the common difference
B) what is the sum of 7th and 11th term ​

Answer 1

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Nth Term in an Arithmetic progression is given by : Nth term=first term + (n-1)d

Here the sum of ist term and 17th term is 40

Therefore a + a+(16)d = 40

2a + 16d = 40

Also ist term + 18 term =43 (given)

a + a + (17)d =43

2a + 17d = 43

Subtract ist equation from ist

D= 3