Age Problem

[charmstot]

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Can anyone help me solve this problem? Are there any shortcuts?

Kim is 1/3 the age of her older sister Sue. In 13 years, Sue will be one year younger than twice Kim's age. How old is Sue?

 

[umc27]

Kim is 1/3 the age of her older sister Sue. In 13 years, Sue will be one year younger than twice Kim's age. How old is Sue?

Set up two equations:

k = (1/3)s

(s + 13) = (2(k+13)) -1

Substitute the value of "k" that you obtain from the first equation into the second equations. Then, solve for "s". It's basically just simple algebra. What makes these problems tricky is converting their wording of the question into the two equations.

 

[DrTacoElf]

I find with these trial and error is easier for me. Start with the middle choice and then go from there 🙂

 

[Sk8aBull]

I find with these trial and error is easier for me. Start with the middle choice and then go from there 🙂

yeah, that seems to be the best method for me as well 🙂

 

[charmstot]

Thanks for the advice, guys.

 

[isd121]

It is not easy to solve all problem with trial and error method.
It is a good idea to learn how to solve this problem by setting equation.

Set up two equations:

1) k = (1/3)s or 3k = s

2) (s + 13)+1 = 2(k+13)

then solve by substituting the value of s from 1st equation in the 2nd equation.
3k+14 = 2k+26
3k-2k = 26-14
k = 12
s=3*12 = 36
answer: k=12 and s=36
it takes less than 30sec to solve it this way 👍

 

[Nismoboy]

wait a minute, how do you do trial and error with this problem, just curious, I would really like to know, maybe it is in fact easier? 😀

 

[DrTacoElf]

Well you have your answer choices. And i usually like to pick on that makes easy fractions. like if one is 36 and 1/3 of 36 is 12 so after 13 years the older ones total age would be 49, and the younger ones' total age would be 12+13 which is 25. 25 x 2 is 50 and 49 is one less so they have to be 36 and 12 initially. It can give you the answer really fast sometimes, but othertimes (especially if they are not whole numbers it can be very tedious).

 

[SrVagas]

Kim is 1/3 the age of her older sister Sue. In 13 years, Sue will be one year younger than twice Kim's age. How old is Sue?[/QUOTE]


my hang up is (Sue + 13) - 1= 2 (Kim + 13)