How many different four-digit numbers can be formed using the digits 1, 4, 5, 6, 7, 8, and 9 if repetition is allowed and ten's position is filled with the perfect square of 3?
542
625
343
595
To calculate the number of different four-digit numbers that can be formed using the digits 1, 4, 5, 6, 7, 8, and 9, with repetition allowed and the ten's position filled with the perfect square of 3, we can proceed as follows:
The perfect square of 3 is 9, so for the ten's position, we have only one option, which is 9.
For the thousands position, any of the seven available digits can be chosen (1, 4, 5, 6, 7, 8, or 9) since repetition is allowed.
For the hundreds position, any of the seven available digits can be chosen.
For the one's position, any of the seven available digits can be chosen as well.
Therefore, the number of different four-digit numbers that can be formed is obtained by multiplying the choices for each position:
Number of choices for the ten's position = 1 (since it is fixed as 9)
Number of choices for the thousands position = 7 (since any of the seven digits can be chosen)
Number of choices for the hundreds position = 7 (any of the seven digits can be chosen)
Number of choices for the one's position = 7 (any of the seven digits can be chosen)
Total number of different four-digit numbers = Number of choices for the ten's position Number of choices for the thousands position
Number of choices for the hundreds position
Number of choices for the one's position
= 1 7
7
7
= 343
Therefore, there are 343 different four-digit numbers that can be formed using the digits 1, 4, 5, 6, 7, 8, and 9, with repetition allowed and the ten's position filled with the perfect square of 3 (9).
Study 40% syllabus and score up to 100% marks in JEE