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Question
Find the sum of the odd numbers between 0 and 50.
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Solution
The odd numbers between 0 and 50 are
1, 3, 5, 7, 9 … 49
Therefore, it can be observed that these odd numbers are in an A.P.
a = 1
d = 2
l = 49
l = a + (n − 1) d
49 = 1 + (n − 1)2
48 = 2(n − 1)
n − 1 = 24
n = 25
`S_n = n/2(a+1)`
`S_25 = 25/2(1+49)`
= `25/2 [50]`
= 25 × 25
= 625
Thus, the sum of odd numbers between 0 and 50 is 625.
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Q.16
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