Question 44: How many three-digit numbers have the sum of the digits equal to 12, the hundreds digit is greater than the tens digit, and the tens digit is greater than the units digit?

Use the relationship between the digits and list the cases that satisfy.

Call the number you are looking for \(\overline {abc}\) with 0≤c**
**

Notice that a + b + c = 9 + 2 + 1 = 8 + 3 + 1 = 8 + 4 + 0 = 7 + 5 + 0

= 7 + 4 + 1 = 7 + 3 + 2 = 6 + 5 + 1 = 6 + 4 + 2= 5 + 4 + 3

There should be nine numbers satisfying the problem condition: 921;831;840;741;750;732;651;642;543

Choose EASY

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