Word Prob: Age of Sarah's younger brother is...?

[MissieMousie]

I'm having a difficult time trying to set this problem up. If you could help, that would be great!

Sarah is twice as old as her youngest brother. If the difference between their ages is 15years, how old is her youngest brother?

I know the answer, I am just uncertain of how to obtain the answer.

I set the problem up as; n being the number.

2n=n-15 (but I think that I am so completely wrong)!

*wrf*

MissieMousie

 

[galactus]

Let B=brother's age and S=Sarah's age.

Sarah is twice her brother's age: 2B=S...[1]

The difference in their ages is 15 yrs: S-B=15...[2]

Sub [1] into [2] and you have: 2B-B=15----->B=15.

Her brother is 15 years old and she is 30 years old

 

[MissieMousie]

*Still not quite understanding this*

I appreciate the reply to this question, but the whole scenario still baffles me!

Thanks!

MissieMousie

 

[Mrspi]

I am not sure what about this scenario confuses you.

You're looking for the brother's age, so
let b = brother's age

Sarah is twice as old as her brother, so
2b = Sarah's age

The difference between their ages is 15.
Sarah's age - brother's age = 15
2b - b = 15

Nothing more to it than that.

 

[MissieMousie]

Thanks!

I think I finally see the correlations. Thanks so much!!