Question
Find the sum of all even natural numbers less than 75.
Answer: Option A
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Required sum = 2 + 4 + 6 + ................+ 74.
This is an A.P. in which a = 2, d = (4 - 2) = 2, `l` = 74.
Clearly , n = 37.
`:.` Required sum = `n/2 (a + l) = 37/2 xx (2 + 74)` = (37 x 38)
= 37 x (40 - 2) = 37 x 40 - (37 x 2)
= (1480 - 74) = 1406
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