Practice!

Sample Problem

What are all the possible 3-digit numbers that can be formed using the given digits 1,5,7 ? (All the digits in each 3-digit number are different.) Write them from smallest to largest

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Solution

Let’s make an organized list. Our rule is: choose the smallest digit possible as we move across the place values from left to right.

If the first digit starts with 1, then the possible numbers are 157 and 175.

If the first digits starts with 5, then the possible numbers are 517 and 571.

If the first digit starts with 7, then the possible numbers are 715 and 751.