(continuation)
Find their present ages.
2007-09-13 19:59:06 · 5 answers · asked by nutellafella 1 in Science & Mathematics ➔ Mathematics
Girls age = x
brothers age = y
(x+2)=(4/5)*(y+2)
(x-4)=(5/7)*(y-4)
Do the algebra and solve for x and y.
HTH
Doug
2007-09-13 20:10:12 · answer #1 · answered by doug_donaghue 7 · 0⤊ 0⤋
Let x be girl's current age
Let y be brother's current age
x + 2 = (4/5)(y + 2) ... (1)
x - 4 = (5/7)(y - 4) ... (2)
From (1)
5x + 10 = 4y + 8
5x - 4y = -2
25x - 20y = -10 ... (3)
From (2)
7x - 28 = 5y - 20
7x - 5y = 8
28x - 20y = 32 ... (4)
(4) - (3)
3x = 42
x = 14
Substitute x = 14 into (3)
25x - 20y = -10
5x - 4y = -2
5(14) - 4y = -2
4y = 70 + 2
4y = 72
y = 18
Hence, girl's present age is 14 and her brother's present age is 18
2007-09-14 03:14:39 · answer #2 · answered by tancy2411 4 · 0⤊ 0⤋
The girl is 14 and her brother is 18.
2007-09-14 03:10:42 · answer #3 · answered by thatnaweedguy 1 · 0⤊ 0⤋
It's another disguised algebra thing g=girls present age, b=brothers present age.
(g+2)/(b+2)=4/5
(g-4)/(b-4)=5/7
rearrange 5g+10=4b+8 and 7g-28=5b-20
so you have two simultaneous equations
5g-4b+2=0
7g-5b-8=0
best of luck
2007-09-14 03:13:41 · answer #4 · answered by Anonymous · 0⤊ 0⤋
She is 14 and her brother is 18.
2007-09-14 03:13:43 · answer #5 · answered by Luis 1 · 0⤊ 0⤋