Question

the sum of 4 th term & 12 term is =20 what is the sum of first 15 terms of AP​

Answer 1

Answer:

The sum of the fourth and twelfth term of an arithmetic progression is 20. What is the sum of the first 15 terms of the arithmetic progression? 15*20/2 =150.

Answer 2

Answer:

150 is the answer....The nth term of any AP is a+(n-1)d were a is the first term and d is the common difference

Sum of AP=n/2(2a+(n-1)d)

Step-by-step explanation:

so 4th term of AP= a+3d

and 12th term = a+11d

As per question above sum is 20 so,

2a+14d=20 i.e. a+7d=10

Now for sum of 15 terms we have

S15=15/2*(2a+14d) {Sum of AP used}=15*(a+7d)=15*10=150