Solution to Q #4

a couple of you have had trouble with Q #4.  here's an explanation:

if the mass weighed 100N in air and then 85N in water, it's % mass in water would be:

[ weight in water / weight in air ] x 100
= [ 85N / 100N ] x 100
= .85 x 100
= 85 %

so the mass only weighs 85% of its initial weight when it's sitting in water.  knowing that %, you could then predict (calculate) how much you would weigh in water if you knew your weight in air, right?