Write the largest 6 digit number having four different digits.

Hint: We have to analyze the problem and solve it using the logic. We will start by finding the largest 6 digit number with only one digit, then the largest 6 digit number having two digits and so on.

Complete step-by-step solution -
The largest 6 digit number with one digit, is the largest 6 digit number itself, which is 999,999.
The largest 6 digit number with two digits can be obtained by replacing the last digit with another number other than 9, that is 8. So the number is 999,998.
Similarly for three different digits, the largest number is 999,987
The largest 6 digit number having four different digits 999,876.
This number has four different digits that are 6, 7, 8 and 9.
This is the required answer.

Note: In such types of questions, no particular formula can be applied. We have to think logically step by step and find the answer. We can find the smallest 6 digit number having four different digits using a similar method-
100,000 - two different digits