Question 628627
The ratio of the present ages of two brother is 1:2
 and 5 years back the ratio was 1:3.
 What will be the ratio of their ages after 5 years?
:
Two brothers ages a & b, now
:
"The ratio of the present ages of two brother is 1:2  
{{{a/b}}} = {{{1/2}}}
Cross multiply
2a = b
:
"5 years back the ratio was 1:3."
{{{(a-5)/(b-5)}}} = {{{1/3}}}
Cross multiply
3(a-5) = b - 5
3a - 15 = b - 5
3a = b - 5 + 15
3a = b + 10
Replace b with 2a
3a = 2a + 10
3a - 2a = 10
a = 10 yrs a's present age
then
2(20) = 20 yrs b's present age
:
"What will be the ratio of their ages after 5 years?"
{{{(10+5)/(20+5)}}} = {{{15/25}}} = {{{3/5}}}; 3:5