How many 3 digit numbers sum will have sum 18?

a) 51 b) 54 c) 61 d) 64

Answer is : B

Solution :

Given :-
1. Number is 3 digitnumber.
2. Sum should be 18.

What To Find:- 
How many such numbers exist?

Procedure :-
Numbers starts with 1  ð 198, 189.................................= 2 numbers
Numbers starts with 2  ð 297, 279, 288..........................= 3 numbers
Numbers starts with 3  ð 396, 387, 378, 369...................= 4 numbers
Numbers starts with 4  ð 495, 486, 477. 468, 459............= 5 numbers
Numbers starts with 5  ð 594, 585, 576. 567, 558, 549.....= 6 numbers
similaly....
Numbers starts with 6  ð 7 numbers

Numbers starts with 7  ð 8 numbers

Numbers starts with 8  ð 9 numbers

Numbers starts with 9  ð 10 numbers

Total Numbers are ð 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 10 = 54