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Thandi is six years older than Sophie. In three years, Thandi will be twice as old as Sophie. How old is Thandi now?

Sagot :

Let's solve the problem step-by-step to find Thandi's current age.

1. Define the variables:
- Let [tex]\( S \)[/tex] represent Sophie's current age.
- Let [tex]\( T \)[/tex] represent Thandi's current age.

2. Set up the equations based on the problem statements:
- We know from the problem that Thandi is six years older than Sophie. Therefore, we can write:
[tex]\[ T = S + 6 \][/tex]

- The second piece of information is that in three years, Thandi will be twice as old as Sophie. This can be translated into the following equation:
[tex]\[ T + 3 = 2 \times (S + 3) \][/tex]

3. Substitute the first equation into the second equation:

Since [tex]\( T = S + 6 \)[/tex], we substitute [tex]\( T \)[/tex] in the second equation:
[tex]\[ (S + 6) + 3 = 2 \times (S + 3) \][/tex]

4. Simplify the equation:
[tex]\[ S + 6 + 3 = 2S + 3 \times 2 \][/tex]
[tex]\[ S + 9 = 2S + 6 \][/tex]

5. Solve for [tex]\( S \)[/tex]:

To isolate [tex]\( S \)[/tex], we bring all terms involving [tex]\( S \)[/tex] to one side of the equation and constant terms to the other side:
[tex]\[ S + 9 - 6 = 2S \][/tex]
[tex]\[ 9 - 6 = 2S - S \][/tex]
[tex]\[ 3 = S \][/tex]

Therefore, Sophie's current age is [tex]\( S = 3 \)[/tex] years.

6. Find Thandi's current age using the first equation:

[tex]\[ T = S + 6 \][/tex]
[tex]\[ T = 3 + 6 \][/tex]
[tex]\[ T = 9 \][/tex]

Thus, Thandi is currently 9 years old.