SOLUTION: 10 years ago, when Su Lin celebrated her birthday with her family, the ratio of the age of Su Lin to Su Lin's sister was 5 : 7. This year, the ratio of the age of Su Lin to Su Lin'

Algebra ->  Customizable Word Problem Solvers  -> Age -> SOLUTION: 10 years ago, when Su Lin celebrated her birthday with her family, the ratio of the age of Su Lin to Su Lin's sister was 5 : 7. This year, the ratio of the age of Su Lin to Su Lin'      Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 1202878: 10 years ago, when Su Lin celebrated her birthday with her family, the ratio of the age of Su Lin to Su Lin's sister was 5 : 7. This year, the ratio of the age of Su Lin to Su Lin's sister is 5 : 6. How old is Su Lin now?


Found 2 solutions by mananth, josgarithmetic:
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
10 years ago, when Su Lin celebrated her birthday with her family, the ratio of the age of Su Lin to Su Lin's sister was 5 : 7. This year, the ratio of the age of Su Lin to Su Lin's sister is 5 : 6. How old is Su Lin now?
let the common multiple be x
10years ago Su lin was 5x years
Her sister was 7x years
after 10 years
Su lin is 5x +10 years
Her sister is 7x +10 years
(5x+10)/(7x+10) = 5/6 ( given condition)
6(5x+10)= 5(7x+10)
30x +60 = 35x + 50
35x-30x=60-50
5x=10
x= 2
Su lin was 2*5 =10 years old 10years ago
Now she is 10+10 = 20 years



Answer by josgarithmetic(39617) About Me  (Show Source):
You can put this solution on YOUR website!
               TenYearsAgo      Today
SuLin          L-10             L
Sister         X-10             X

Ratio         5/7               5/6

system%28%28L-10%29%2F%28X-10%29=5%2F7%2CL%2FX=5%2F6%29

7%28L-10%29=5%28X-10%29
7L-70=5X-50
7L-5X=20


L%2FX=5%2F6
6L=5X

Substitution:
7L-6L=20
highlight%28L=20%29-----------Su Lin now.