#3 Permutations and Combinations.
Probability
Level
1
How many numbers lying between 100 and 1000 can be formed with the digits 0, 1, 2, 3, 4, 5, if the repetition of the digits is not allowed?
The answer is 100.
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1 solution
All the numbers lying between 100 and 1000 are three digit numbers.So out of the six numbers provided we could fill the hundred's place by five numbers(bcz if zero occupies hundred's place, the number become two digit).
Likewise, ten's place can be filled by five numbers(which doesn't include the number assigned to hundred's place as repetition is not allowed).
And one's place can be filled with four numbers(which doesn't include the number s assigned to hundred's and ten's place as repetition is not allowed)
So total possible numbers that can be formed = 5 × 5 × 4 = 100