Math, asked by jusstudy, 1 year ago

If 21st term of an A.P is 25,find the sum of its first 41 terms.....
plzzz answer fast....

Answers

Answered by Anonymous
1
Hola there...
According to the question,

a21 = 25

=> a + 20d = 25

We now have to find the sum of 41 terms so,

Sn = n/2 (2a + (n - 1)d)

=>S41. = 41/2 (2a + (41 - 1)d)

=> S41 = 41/2(2a + 40d)

=> S41 = 41(a + 20d)

=> S41 = 41 × 25

=> S41 = 1025. ....Ans

Hope this helps....:)
Answered by Shivamu509
2
25 =a+20d: 50=4a+40d

S(41)= (41/2)[2a+40d]

S41=20.5[50]=1025
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