find the sum of first 22 terms of an AP in which d =7 and 22nd term is 149.
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GIVEN :
Common Difference of an AP = d = 7
22nd term of an AP = 149
In an AP nth term = a + (n - 1)d
149 = a + (22 - 1)7
149 = a + (21)7
149 = a + 147
a = 149 - 147
a = 2
First term (a) = 2
In an AP sum of the terms = n/2 [ a + an ]
= n/2 [ a + an ]
= 22/2 [ 2 + 149 ]
= 11 [ 151 ]
= 1661
Therefore, the sum of 22 terms is 1661.
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