Inelastic car collision, answers aren't matching up

[BananasAreCool]

Homework Statement

Car A, having a mass of 1.30 x 10+3kg is traveling at 60.0 km/h due east when it collides with car B, having a mass of mass 1.70 x 10+3kg traveling at 40.0 km/h due west. If the collision is totally inelastic, find the final velocity of car B.
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Homework Equations

I'm using the equation

m1v⃗ 1+m2v⃗ 2=(m1+m2)v⃗ f​

The Attempt at a Solution

I'm getting 146,000 = (3000)Vf which I'm then dividing to get a velocity of 48.66. But the answer key is telling me 3.33km/h due east. I haven't taken physics in years and am super rusty so any help would be much appreciated.

 

[gneill]

Hi BananasAreCool, Welcome to Physics Forums.

Did you take into account the fact that the cars are traveling in opposite directions?

 

[BananasAreCool]

Hi BananasAreCool, Welcome to Physics Forums.

Did you take into account the fact that the cars are traveling in opposite directions?

That's what I was thinking was the problem, what is the equation for them moving in opposite directions?

 

[BananasAreCool]

That's what I was thinking was the problem, what is the equation for them moving in opposite directions?

I was just able to figure it out, I had to subtract instead of add the two so instead of getting 146,000 I got 10,000, which divided by 3,000 equals to 3.33km/h.

 

[gneill]

I was just able to figure it out, I had to subtract instead of add the two so instead of getting 146,000 I got 10,000, which divided by 3,000 equals to 3.33km/h.

Yup. Well done.