# Homework Help: Fraction question

1. Nov 14, 2006

### sapiental

Hey,

I'm terrible with fractions and would appreciate any help regarding this problem.

This is a problem from my physics course.

F2 = [ (v + v2)/(v + v1) ] F1

I need to solve for v1. I am given the values for F2, v, v2, and F1 and need to turn the formula around to solve for v1..

F1 = 400
F2 = 420
v = 344
v2 = 26.82

My attempt was F2/(F1(v+v2)) = 1 / (v+v1)

but this is wrong..

any suggestions?

2. Nov 14, 2006

$$F_{2} = \left \frac{v+v_{2}}{v+v_{1}}\right F_{1}$$
So $$F_{2}(v+v_{1}) = F_{1}(v+v_{2})$$
$$v + v_{1} = \frac{F_{1}(v+v_{2})}{F_{2}}$$
$$v_{1} = \frac{F_{1}(v+v_{2})}{F_{2}} - v$$