What is the OA?The procedure is what i need to know!
You can, for example never foretell what any one man will do, but you can say with precision what an average number will be up to!
The fastest approach here might be to plug in the answer choices.James is twice as old as Stephanie, who, 4 years ago, was 3 times as old as Kate. If, 5 years from now, the sum of their (all 3 people) ages will be 51, how old is Stephanie?
A) 6
B) 10
C) 14
D) 20
E) 24
Having said that, here's one possible algebraic approach.
Let x = Stephanie's present age.
James is twice as old as Stephanie
So 2x = James' present age.
4 years ago, Stephanie's was 3 times as old as Kate
In other words, 4 years ago, Kate's age was 1/3 of Stephanie's age.
4 years ago, Stephanie'sage was x-4, so Kate's age 4 years ago, was (x-4)/3
So, Kate's present age = (x-4)/3 + 4
In 5 years . . .
Stephanie's age = x + 5
James' age = 2x + 5
Kate's age = (x-4)/3 + 4 + 5
5 years from now, the sum of their ages will be 51
So (x + 5) + (2x + 5) + (x-4)/3 + 4 + 5 = 51
Simplify: 3x + (x-4)/3 + 19 = 51
Subtract 19 from both sides: 3x + (x-4)/3 = 32
Multiply both sides by 3: 9x + (x-4) = 96
Solve . . . [spoiler]x = 10[/spoiler]
Answer: B
If anyone is interested, we have a free video on solving word problems involving past and future ages: https://www.gmatprepnow.com/module/gmat- ... ems?id=908
Cheers,
Brent
