# Just a quick physics question

$$K = 1/2(1300kg)(10km/h)^2 + 1/2(1600kg)(6.6km/h)^2-1/2(2900)(8.12)^2 = 320J$$

how is that 320J? when i plug that into my calculator, i get 4243.12(not sure what units this is in). can someone tell me why that K is 320 j?