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

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)

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now if x is 9 then y has 1 option (that is 0)

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