Question

the sum of all the digit of the numbers from 1 to 100is a. 5050 b. 903 c. 901 d. 900

Answer 1

Answer:

(a) 5050

Step-by-step explanation:

The sequence 1, 2, 3, ..., 100 is an AP with a = 1, d = 1, n = 100

Hence, sum of n terms :

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

= [ 100 / 2] [ 2 ( 1 ) + ( 100 - 1 ) 1 ]

= 50 [ 2 + 99 ]

= 50 [ 101 ]

= 5050

Answer 2

n(n+1)/2

=100(100+1)/2

=50*101

=5050