Can i get and an explanation on c?

1.67 m/s

Explanation:

Momentum is conserved.

Initial momentum = final momentum

(30 kg) (10 m/s) + (35 kg) (-10 m/s) = (30 kg) v + (35 kg) (0 m/s)

300 - 350 = 30v

v = -5/3 m/s

Linus will move at 1.67 m/s in the direction opposite that he started.

measuring things 1 litre of water

305.7

explanation:

density =m/v

density =917/3.00

density = 305.

approximately = 305.7

in four significant figures