Question 575473
let g = daughter's present age
let b = brother's present age
let f = father's present age
;
Write an equation for each statement:
:
"A girl is twice as old as her brother
g = 2b
" and half as old as her father."
g = .5f
:
"In 50 years, her brother will be half as old as his father."
b + 50 = .5(f+50)
b + 50 = .5f + 25
b = .5f + 25 - 50
b = .5f - 25
We can replace .5f with g
b = g - 25
we can replace g with 2b
b = 2b - 25
25 = 2b - b
b = 25 is brothers age
then
2(25) = 50 yrs is the daughter's present age
;
:
Check this using the third equation: that makes the father 100 yrs old
in 50 years: 25 + 50 = .5(100+50); checks out anyway