Question

Sum of the first 12 terms of an AS is 240. Then the sum of its first term and 12th term is​

Answer 1

Answer:

if a is the 1st term and bis the common difference then

12/2(2a+11b)=240

2a+11b=240×2/12=40

sum of 1st term and 12th term is

a +a+(12-1)b

=a+a+11b

=2a+11b=40

Answer 2

ANSWER:

Then the sum of its first term and 12th term is 40

Step-by-step explanation:

Let the first term of the AP is 'a' and last term is 'l'.

Total number of terms are n( here n=12 given)

REQUIRED FORMULA:

Arithmetic Sum = n/2×(a+l)

From the given condition

12/2×(a+l) = 240

6(a+l)=240

(a+l)=40

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