How many terms of the A.P 43,
39, 35, ................. be taken so that
their sum is 252?
12
16
18
Answers
Answered by
5
Given first term(a) = 43
Common difference(d) = 39 - 43 = -4
Sum upto n terms of an AP = n/2 {2a + (n-1)d}
where n is no of terms
=> n { 2a + (n-1)d } /2 = 252
=> n { 2(43) + (n-1)(-4) } = 504
=> n { 86 - 4n + 4 } = 504
=> 86n - 4n^2 + 4n = 504
=> -4n^2 + 90n - 504 = 0
=> -4n^2 - 42n - 48n - 504 = 0
=> -2n ( 2n + 21) -24 ( 2n + 21 ) = 0
=> ( 2n + 21 )( -2n - 24) = 0
=> n = -21/2 (or) n = 12
∴ No of terms are 12 because no of terms can't be in decimals
Answered by
0
Answer:
your answer is 12
Step-by-step explanation:
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