Question

Find the sum of the odd numbers between 0 and 50.

Answer 1

Odd numbers between 0 and 50 are 

1 + 3 + 5 + 7 + ……… + 49 = ? 

Here. a = 1, d = a₃ – a₁= 3 – 1 = 2 

a_n = 49, n =?, S = ? 

a_n = a + (n – 1) d = 49 

= 1 + (n – 1)2 = 49 

1 + 2n – 2 = 49 

2n – 1 = 49 

2n = 49 + 1 

2n = 50

= 25 × 25 

∴ S₂₅ = 625