Arithmetic Ability
Permutations and Combinations

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Q.

How many 3-digit numbers can be formed with the digits 1,4,7,8 and 9 if the digits are not repeated ?

View Answer

Correct choice: A

Explanation:

Three digit number will have unit’s, ten’s and hundred’s place. Out of 5 given digits any one can take the unit’s place. This can be done in 5 ways. ... (i) After filling the unit’s place, any of the four remaining digits can take the ten’s place. This can be done in 4 ways. ... (ii) After filling in ten’s place, hundred’s place can be filled from any of the three remaining digits. This can be done in 3 ways. ... (iii) So,by counting principle, the number of 3 digit numbers = 5x 4 x 3 = 60
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