Question

Find the sum of first 20terms of the Arithmetic progression 3+6+9+.................​

Answer 1

Question:-

Find the sum of first 20terms of the Arithmetic progression 3 + 6 + 9 + _________

Solution:-

To find the sum of nth term of A.P we have to use

»»» Sn = n/2 [ 2a + (n - 1)d ]

• first term = 3
• common difference = t2 - t1
• => 6 - 3 = 3

➣ S 20 = 20/2 [ 2(3) + (20 - 1)3 ]

➣ S 20 = 10 [ 6 + 57 ]

➣ S 20 = 10(63)

➣ S 20 = 630

∴ ✐ 20th term of A.P is 630