Discussion :: Numbers
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The sum all even natural numbers between 1 and 31 is:
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Answer : Option C
Explanation :
Required sum = (2 + 4 + 6 + ... + 30)
This is an A.P. in which a = 2, d = (4 - 2) = 2 and l = 30.
Let the number of terms be n. Then,
tn = 30 
a + (n - 1)d = 30
2 + (n - 1) x 2 = 30
n - 1 = 14
n = 15
Sn =\(\frac { n } { 2 }(a+1) \)=\(\frac { 15 } { 2 }* (2+30)\)=240
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