Coefficient of friction and drunk driver

[smw1016]

Homework Statement

A drunk driver in a 2400kg car plows into a 1200kg parked car with its brake set. Police measurements show that the two cars skid together a distance of 25m before stopping.

If the effective coefficient of friction is 0.70, how fast was the drunk going just before the collision?

Homework Equations

Mv^2 / 2 = (M+m)μg * S i used this equation

2400*v^2/2=(2400+1200)*.70*25m

and i got 7.246 for v

what did i do wrong?

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[Rake-MC]

It looks to me like when you subbed in your values for the equation, you forgot acceleration due to gravity.