SOLUTION: three years ago mary was three times as old as her sister. now mary is twice as old as her sister. how old is mary now.
please show work
Algebra.Com
Question 100104: three years ago mary was three times as old as her sister. now mary is twice as old as her sister. how old is mary now.
please show work
Answer by ptaylor(2198) (Show Source): You can put this solution on YOUR website!
Let x=Mary's age now
And let y=her sister's age now
Then x-3=Mary's age three years ago
Now we are told that x-3=3(y-3)------------------eq1
and that:
x=2y-------------------------------------------------eq2
substitute x=2y into eq1 and we get:
2y-3=3(y-3) get rid of parens
2y-3=3y-9 add three and subtract 3y from both sides
2y-3y-3+3=3y-3y-9+3 collect like terms
-y=-6 divide both sides by -1
y=6--------------------Mary's sister's age now
substitute into eq2
x=2*6
x=12-----------------Mary's age now age now
CK
x-3=3(y-3)
12-3=3(6-3)
12-3=3*3
9=9
also
12=2*6
12=12
Hope this helps---ptaylor
RELATED QUESTIONS
Three years ago Mary was three times as young as her father. Today Mary's father is 12... (answered by ewatrrr)
Three years ago, Mary was seven times as old as her sister Jane was. Two years ago, Mary (answered by scott8148)
Mary is three times as old as her sister. How old will the sister be when Mary is at... (answered by ikleyn)
How would you solve this? Mary is presently 12 years older than her sister. Four years... (answered by stanbon)
mike is three times as old as his little sister mary. in four years hell be twice as old... (answered by Alan3354)
mike is three times as old as his little sister, Mary. in 4 years, he will be twice as... (answered by Alan3354)
Mike is three times as old as his little sister mary. in four years, he will be twice as... (answered by jorel1380)
five years ago, sue was five times as old as her sister. sue is three times as old as her (answered by stanbon)
5 years ago Sue was 5 times as old as her sister Sue is three times as old as her sister... (answered by Alan3354,stanbon)