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Question

The first and the last terms of an AP are 17 and 350 respectively. If the common difference is 9, then find the number of terms in the AP and their sum.


A

32; 6973

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B

38; 6973

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C

32; 7114

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D

38; 7114

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Solution

The correct option is B

38; 6973


Given,
First term =a=17

Last term =l=350

Common difference =d=9

Using formula an=a+(n1)d, we can say that

350=17+(n1)(9)

350=17+9n9

342=9n

n=3429=38

Applying formula, Sn=n2(2a+(n1)d), we get

S38=382(34+(381)9)

S38=19(34+333)=6973

Therefore, there are 38 terms and their sum is equal to 6973.


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