The sum of first 45 natural numbers is: Answers.
A) 1035	B) 1038	C) 1040	D) 1045	E) 1050
Let Sn =(1 + 2 + 3 + ... + 45). This is an A.P. in which a =1, d =1, n = 45.   Sn = n [2a + (n - 1)d] = 45 x [2 x 1 + (45 - 1) x 1] = 45 x 46 = (45 x 23)   2 2 2   = 45 x (20 + 3)   = 45 x 20 + 45 x 3   = 900 + 135= 
<gadget id="calculator">900 + 135</gadget>
<output>1_035</output>
1035.   Shorcut Method:   Sn= n(n + 1) = 45(45 + 1) = 1035.   2 2   1035
<result>A</result>
The sum of first 45 natural numbers is: