5. find the sum of the first 50 common terms of 12 16 20 ... and 18 24 30 ....
Answers
Answered by
5
This is a question on the sum of the first n terms of an arithmetic progression :
1.) The first sequence, 12 16 20
The formula for the sum is :
Sn = n(a₁ + an) /2
a₁ = the first term
an = the last term
an = a₁ + (n - 1)d
d = the common difference
d = 4
a₁ = 12
n = 50
a₅₀ = 12 + 49 × 4 = 208
S₅₀ = 50(208 + 12) / 2 = 5500
2.) The second sequence, 18 24 30
an = 18 + 49 × 6 = 312
S₅₀ = 50(18 + 312) / 2 = 8250
Similar questions