SOLUTION: The ages of a brother and sister are 11 and 8 years. In how many years' time will the product of their ages be 378?

Click here to see ALL problems on Age Word Problems

Question 942537: The ages of a brother and sister are 11 and 8 years.
In how many years' time will the product of their ages be 378?

Found 2 solutions by macston, josmiceli:
Answer by macston(5194) (Show Source):
You can put this solution on YOUR website!
(11+X)(8+X)=378

Solved by pluggable solver: SOLVE quadratic equation with variable

Quadratic equation (in our case ) has the following solutons:

For these solutions to exist, the discriminant should not be a negative number.

First, we need to compute the discriminant : .

Discriminant d=1521 is greater than zero. That means that there are two solutions: .

Quadratic expression can be factored:

Again, the answer is: 10, -29. Here's your graph:

The solutions to the equation are 10 and -29, the relevant solution here is the 10
In 10 years,the product of their ages will be 378

Answer by josmiceli(19441) (Show Source):
You can put this solution on YOUR website!
Let = the number of years from now
when the product of their ages is
----------------

I can use the quadratic formula

( notice that I can only use the + square root )
In 10 years, the product of their ages will be 378
------------------
check:

OK