Math, asked by riya190, 1 year ago

question 20 is the sum is 19926

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Answered by Monu631
0
Here, a= 4
l = 81
d= 7
To find n,we will apply the formula
l = a+(n-1)d
By putting the value,you will find
n = 12.
Now, By using the formula
S= n/2(a+l)
S = 510.
d=
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