My Math Forum  

Go Back   My Math Forum > High School Math Forum > Elementary Math

Elementary Math Fractions, Percentages, Word Problems, Equations, Inequations, Factorization, Expansion

LinkBack Thread Tools Display Modes
October 3rd, 2007, 10:49 PM   #1
Joined: Sep 2007

Posts: 4
Thanks: 0

word problem

At present sum of the age of three sister is 68 years. Four year ago the ratio of their ages are 3:4:7. Find the age of the middle sister after 5 years.
chak_2007 is offline  
October 4th, 2007, 12:22 AM   #2
Global Moderator
Joined: Dec 2006

Posts: 20,629
Thanks: 2077

So four years ago their ages were 12, 16, and 28, and at present their ages are 16, 20 and 32. Add 5 onto whichever set of ages you think the question is referring to or just the age of the "middle" sister if you know which one that is.
skipjack is offline  
October 4th, 2007, 07:16 PM   #3
Senior Member
Joined: Apr 2007

Posts: 2,140
Thanks: 0

We can either solve this math problem using some arithmetic, or both in arithmetic and algebraic terms. I'll pick both arithmetic and algebraic.
At present, there were three sisters. One sister is a years old, second sister is b years old, and the third sister is c years old. Therefore, we have
a+b+c=68 years. Four years ago, the three sisters' age were
a-4years, b-4years, and c-4years. Thus, the total age of the three sisters four years ago is
(a-4years)+(b-4years)+(c-4years)=68 years-12 years=56 years.
Add all the numbers up in the ratio... which is 3+4+7=14.
Divide 56 years by 14, which givew 4. Therefore, we have three sisters that have ages of 12 years, 16 years, and 28 years (4 years ago).
We can assume any algebraic variable for these numbers, so I'll pick
a=16 years, b=20 years, and c=32 years (thus, these are the ages of three sisters' at present).
Middle sister is b=20 years (a<b<c), so therefore, after five years, the age of the middle sister is b+5years=20years+5years=25 years.
johnny is offline  

  My Math Forum > High School Math Forum > Elementary Math

problem, word

Search tags for this page
Click on a term to search for related topics.
Thread Tools
Display Modes

Similar Threads
Thread Thread Starter Forum Replies Last Post
ANOTHER... word problem! angelina Elementary Math 7 August 9th, 2010 11:18 PM
Word problem hemi Algebra 3 September 15th, 2009 03:48 PM
Word Problem Hello Elementary Math 3 September 6th, 2008 04:47 AM
Word Problem iReap Algebra 2 February 10th, 2008 06:37 PM
word problem chak_2007 Elementary Math 5 September 13th, 2007 04:23 AM

Copyright © 2019 My Math Forum. All rights reserved.