How do I change 14.99398 mi into three significant figures

Asolution contains 180 g of glucose (c6h12o6) and 162 g of water. what is the mole fraction of glucose?

If you add 5.00 ml of 0.100 m sodium hydroxide to 50.0 ml of acetate buffer that is 0.100 m in both acetic acid and sodium acetate, what is the ph of the resulting solution? acetic acid: ka = 1.8. x 10-5

Is a pencil falling to the floor anon contact force, a force, or a contact force