Question

the sum of 3 numbers in an ap is 12 and sum of first 4 terms is 24 . find the sum of its first 10 terms

Answer 1

Answer:

180

Step-by-step explanation:

part 1:

n=3

sum=12

n/2[2a+(n-1)d]=12

3/2[2a+2d]=12

a+d=4 --->(1)

part 2:

n=4

sum=24

n/2[2a+(n-1)d]=24

4/2[2a+3d]=24

2a+3d=12---->(2)

solving (1) and (2)

we get a=0, d=4

sum of 10 terms = 10/2[0+(10-1)4]

=180