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  1. The sum of first 50 odd natural numbers is
    1. 1000
    2. 1250
    3. 5200
    4. 2500
Correct Option: D

S = 1 + 3 + 5 + ..... to 50 terms Here, a = 1
d = 3 – 1 = 2
n = 50

∴  S =
n
[2a + (n − 1)d]
2

=
50
[2 × 1 + (50 − 1) × 2]
2

= 25 (2 + 98) = 25 × 100
= 2500


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