Question 1174861
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The statement of the problem suggests that there is only one number that satisfies the condition of the problem.<br>
From the wording of the problem, we know the units digit is the smallest.  So start with the smallest possible units digit, which is 0.<br>
That makes the tens digit 0+2=2; and that makes the hundreds digit 2+1=3.  That gives us the number 320.<br>
And we can see that, if we had started with any digit greater than 0 for the units digit, we would have ended up with a number greater than 400.<br>
So 320 is the only number that satisfies all the conditions.<br>