and we have to find his sisters present age.i nees formula
2007-09-13 05:58:57 · 4 answers · asked by i love.. 1 in Science & Mathematics ➔ Mathematics
let y be the sisters present age.
2(y-5)=x-5
2y-10=x-5
2y=x+5
2007-09-13 06:05:43 · answer #1 · answered by Andrew M 2 · 0⤊ 0⤋
x-5 = 2s
x= 2s+5 You can say the boy 5 years older than twice his sister's age.
But to get actual number you need another equation.
You need to know more information.
If there are two unknown quantities, you need to be able to write down two independent equations in order to get numerical solutions.
2007-09-13 06:07:23 · answer #2 · answered by Anonymous · 0⤊ 0⤋
if 5 years ago he was twice as old as his sis, then he WAS x-5. so his sister WAS 1/2(x-5) so his age NOW is x, and his sis is 1/2x+2.5 so just plug his age in as x.
2007-09-13 06:08:25 · answer #3 · answered by Prove god, then we'll talk. 3 · 0⤊ 0⤋
2(y - 5) = x - 5
2y - 10 = x - 5
2y = x + 5
y = (x + 5)/2
You don't have enough information to solve this.
2007-09-13 06:10:01 · answer #4 · answered by gebobs 6 · 0⤊ 0⤋