The square of Mark's age 3 years ago is 6 times the age he will be in 9 years. What is his age now?

Alaina Durham

Alaina Durham

Answered question

2023-01-20

The square of Mark's age 3 years ago is 6 times the age he will be in 9 years. What is his age now?

Answer & Explanation

Elianna Bradley

Elianna Bradley

Beginner2023-01-21Added 8 answers

We can create an equation to be solved if we represent Mark's current age as x.
We know that (x3)2, "the square of his age three years ago", is 6 times greater than "his age in 9 years", (x+9), so to make this problem solvable we must create an expression where these two equal each other.
Thus by multiplying (x+9) by 6, we set "his age in 9" years to be equal to "the square of his age 3 years ago", creating the following expression:
(x3)2=6(x+9)
Which, after being streamlined, results in a quadratic equation:
x212x45=0
0=(x15)(x+3)
Hence the two possible answers are:
x1=15 and x2=3
Obviously, you cannot be -3 years old, so he must be 15 years old.

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