SOLUTION: Mary is three times as old as susan. Two years ago, the sum of their ages was twenty. How old are they now

Algebra ->  Customizable Word Problem Solvers  -> Age -> SOLUTION: Mary is three times as old as susan. Two years ago, the sum of their ages was twenty. How old are they now       Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 1056553: Mary is three times as old as susan. Two years ago, the sum of their ages was twenty. How old are they now
Answer by ikleyn(52784) About Me  (Show Source):
You can put this solution on YOUR website!
.
Mary is three times as old as susan. Two years ago, the sum of their ages was twenty. How old are they now
~~~~~~~~~~~~~~~~~~~~~~~~~~ 

The condition is this system of two equations

M = 3S,               (1)    ("Mary is three times as old as susan.")
(M-2) + (S-2) = 20.   (2)    ("Two years ago, the sum of their ages was twenty.")

Substitute the expression 1) into equation (2). You will get

(3S -2) + (S-2) = 20,

4S - 4 = 20,

4S = 24,

S = 24%2F4.

S = 6.  Susan is 6 years old.

Then Mary is 3*6 = 18 years old.

There is a bunch of lessons on age word problems
    - Age problems and their solutions
    - A fresh formulation of a traditional age problem
    - Really intricate age word problem
    - Selected age word problems from the archive
in this site.

Read them and become an expert in solving age problems.

Also, you have this free of charge online textbook in ALGEBRA-I in this site
    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.

The referred lessons are the part of this online textbook under the topic "Age word problems".