Aptitude Interview Question:

In how many ways can a lock be opened if that lock has three digit number lock if
i) the last digit is 9
ii) and sum of the first two digits is less than or equal to the last digit

Submitted by: Administrator

our number is xy9
now if x is 0 then y has 10 options
now if x is 1 then y has 9 options (except 9)
now if x is 2 then y has 8 options (except 9 and 8)
.
.
.
now if x is 9 then y has 1 option (that is 0)
Submitted by: Administrator