Question

What is the sum of all ten digit numbers formed with 0 to 9?

Answer 1

0,1,2,3,4,5,6,7,8,9

all are in AP

so

a = 1

n = 10

tn = 9

d = 1

formula of sum of N term in Ap

Sn = n/2[2a + (n - 1)d]

Now put the value in Above equation .

Sn = 10/2 [0+ 9]

Sn = 5*9 = 45