Question

The sum of 15 terms is390 and forst term is 12 then the difference is

Answer 1

Answer:

2

Step-by-step explanation:

S=390

n=15

a=12

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

         390=(15/2)[2*12+(15-1)d]

          390=7.5(24+14d)

          390/7.5=24+14d  

          52-24=14d

          28=14d

          d=2