Question

find the sum of all even natural numbers less than 75

Answer 1

we have a formula that is n(n+1)/2
here=75
75(76)/2
75(38)
2850

Answer 2

Hii There!!!

According to the question,

A.P becomes :- 2 , 4 , 6 , .... , 74


Here, a = 2 , d = 4 - 2 = 2 , an (or) l = 74 , n = ? , Sn = ?


Since, an = a + ( n - 1 ) d

=> 74 = 2 + ( n - 1 ) 2

=> 74 - 2 = ( n - 1 ) 2

=> 72 / 2 = n - 1

=> 36 = n - 1

=> n = 37


Now, We know that
Sn = n/2 [ a + l ]

=> Sn = 37 / 2 [ 2 + 74 ]

= 37 / 2 [ 76 ]

= 1406


Hence, Sn = 1406



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