PreCalculus - Algebra Fundamental Review (24 of 80) Review of Word Problems: Ages

In this video I will find how much how old are Dad and his son if 5 years ago a dad was 6 years older than 3 times his son's age at that time.

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For anyone watching in the future, thrt4ick is usually set-up, and in this case that's knowing to express on of the variables in terms of the other.

This is analogous to solving one of 2 equations for x in terms of y or vise versa, and plugging it into the other. If interest I = .45x + .60y, we have nowhere to go without first solving one of them like this.

[gregw]

I would have never thought to do all of this just from reading a word problem. Colleges teach precalc from an online software and it doesn't show you how to get the answer. It expects you to know how to do everything with zero explanation

[carnivalwrestler]

Very nice, clear explanation. Thank you for all your work.

[MM-qkeg]

I did something a bit easier. So I defined x as the son's age today and y as the dad's age today. then I came up with two equations, one in 5 years ago and one 4 years from now. Then I set them as equal and found x. ( 3x-4=2x+9) and once I had x, I put in back in the equation and I had y as well. it was very easy and not at all complicated.

[jamesmorrison]

Well I just made one equation out of this. Just taking now as the past viewpoint and then setting 3x+6-5= 2x+5+4 (-5 years == 5 years ago and +4 years from now) and then solving for x gives me 8. 8+5 years=13years./Plugging in for Dad=35years.