Question

Find the sum 24 + 28 + 31 +.........+ 100

Answer 1

Answer:

a₁=24

a₂=28

aₙ=100

d=a₂-a₁

  =28-24

   =4

aₙ=a+(n-1)d

100=24+(n-1)4

100-24=(n-1)4

76=(n-1)4

76/4=n-1

19+1=n

20=n

n=20

sₙ=n/2(a+aₙ)

s₂₀=20/2(24+100)

s₂₀=10(124)

s₂₀=1240