1+2+3+4+5+6+7+8+9+10+11+12+13+14+15+16+17+18+..............+100 =

1 + 2 + 3 + 4 + ... + 100
a = 1
b = U₂-U₁
b = 2 - 1
b = 1

Sₙ=n/2 ( a + Uₙ)
S₁₀₀=100/2 ( 1 + 100 )
S₁₀₀ = 50 (101)
S₁₀₀=5050

caranya=100+1=101,99+2=101,98+3=101+..........
kesimpulannya adalah (100÷2)×101=50×101=5.050