Question

can someone help me out with this maths?
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Answer 1

Answer:

648

Step-by-step explanation:

Using Permutations and combinations, we observe that:

the first digit maybe chosen from 0 to 9 i.e. 9 options.

Likewise the second spot maybe filled by numbers ranging from 0 to 9 and must not be the first digit i.e. 9 options

and the third slot may be filled in 8 ways (from numbers ranging from 0 to 9 but not equal to the first or second digit)

Therefore the number of numbers between 100 and 999 with all different digits is 9*9*8=648