Question

find sum of all 3D three digit natural numbers which are divisible by 13​

Answer 1

Answer:

37674

Step-by-step explanation:

a, first 3digit 13 multiple =  104

l = last 3digit 13 multiple =  988

d = 13

therefor no. of 3 digit 13 multiples n = [(l-a)/d] + 1

                                                            = [(988-104)/13] + 1

                                                            = [884/13] + 1 = 68+1 = 69

=> sum of all 3digit 13 multiples = Sn = (n/2)*[a+l]

                                                             = (69/2)[104+988] = (69/2)*1092

                                                             = 69*546 = 37674