Question

Find the sum of the unit digits of first 99 whole numbers

Answer 1

Answer:

450

Step-by-step explanation:

The numbers to look at are

1, 2, 3, ..., 10,

11, 12, 13, ..., 20,

...

91, 92, 93, ...., 99.

The sum we want is then

1 + 2 + 3 + ... + 9 + 0    [ numbers 1 to 10, group 1 ]

+ 1 + 2 + 3 + ... + 9 + 0  [ numbers 11 to 20, group 2 ]

+ 1 + 2 + 3 + ... + 9 + 0  [ numbers 21 to 30, group 3 ]

+...

+ 1 + 2 + 3 + ... + 9   [ numbers 91 to 99, group 10 ]

= ( 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 ) × 10

= 45 × 10

= 450

Answer 2

Answer:

nmtc ka question number 32 chapter 1