Question

Find the sum of first 20 terms of the arthmetic sequence 5,8,11,14

Answer 1

Answer:

670

Step-by-step explanation:

given A.P is 5,8,11,14

=> a=5, d=8-5=3 , n=20

find S₂₀

Sₙ = n/2 [ 2a + (n-1) d ]

S₂₀ = 20/2 [ 2(5) + (19) 3 ]

      = 10 (10+57)

     = 10(67)

    = 670