What is the sum of the first 20 terms of an A.P ..,if a= 4 and t20 = 36 ?
A) 40
B) 200
C) 400
D)800
explain..
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Answer:
Given,
a= 4
20th term or last term for finding sum = 36
number of term = 20
Sum of n term =
(a + l) \times n \div 2
where
a= first term = 4
l = last term = 36
and n = no. of terms = 20
After substituting value
Sum = (4 + 36)X 20/2
= 40 X 10
= 400
Step-by-step explanation:
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