In a three-digit number, the tens digit is the same as the hundreds digit. The ones digit of this number is equal to [tex]$\frac{1}{3}$[/tex] of the sum of the other two digits. Find the number if the sum of all its digits is equal to 24.



Answer :

Let's define the digits of the three-digit number:
- Let [tex]\( h \)[/tex] be the hundreds digit.
- Let [tex]\( t \)[/tex] be the tens digit.
- Let [tex]\( u \)[/tex] be the units (ones) digit.

Given the following conditions:
1. The tens digit [tex]\( t \)[/tex] is the same as the hundreds digit [tex]\( h \)[/tex], thus [tex]\( t = h \)[/tex].
2. The ones digit [tex]\( u \)[/tex] is equal to [tex]\(\frac{1}{3}\)[/tex] of the sum of the hundreds digit [tex]\( h \)[/tex] and the tens digit [tex]\( t \)[/tex]. Hence, [tex]\( u = \frac{1}{3}(h + t) \)[/tex].
3. The sum of all its digits is equal to 24, i.e., [tex]\( h + t + u = 24 \)[/tex].

Step-by-step solution:

1. Based on the first condition, we have [tex]\( t = h \)[/tex].
2. Substituting [tex]\( t = h \)[/tex] into the second condition gives:
[tex]\[ u = \frac{1}{3}(h + h) = \frac{1}{3}(2h) = \frac{2h}{3} \][/tex]
3. Now, substituting [tex]\( t = h \)[/tex] and [tex]\( u = \frac{2h}{3} \)[/tex] into the third condition, we get:
[tex]\[ h + h + \frac{2h}{3} = 24 \][/tex]
Simplifying this equation:
[tex]\[ 2h + \frac{2h}{3} = 24 \][/tex]
To clear the fraction, multiply every term by 3:
[tex]\[ 3(2h) + 3\left(\frac{2h}{3}\right) = 3 \cdot 24 \][/tex]
[tex]\[ 6h + 2h = 72 \][/tex]
[tex]\[ 8h = 72 \][/tex]
Solving for [tex]\( h \)[/tex]:
[tex]\[ h = \frac{72}{8} = 9 \][/tex]
4. Since [tex]\( t = h \)[/tex], we have [tex]\( t = 9 \)[/tex].
5. Using [tex]\( h = 9 \)[/tex], find [tex]\( u \)[/tex]:
[tex]\[ u = \frac{2h}{3} = \frac{2 \cdot 9}{3} = \frac{18}{3} = 6 \][/tex]

So, the three-digit number is made up of digits:
- Hundreds digit: [tex]\( 9 \)[/tex]
- Tens digit: [tex]\( 9 \)[/tex]
- Units digit: [tex]\( 6 \)[/tex]

The number is thus [tex]\( \boxed{996} \)[/tex].

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