The initial water volume in this container was 10.0ml. when the key was submerged, 3 volumes of displaced water were collected: 0.7ml, 0.8 ml and 0.9 ml. what is the volume of the key

explanation: look here

one person pulls 90n one way and the other has 100n pulling the other way.

so the net force = 90 - 100 = -10n,

or the ans can be 10n if the picture shows -90n and 100n instead.

answer: 2×10^-2kg

explanation: density= mass per volume

vol=mass/density

converting to s.i units we have;

3÷1000kg = 0.003

1.5÷100m = 0.15

0.003/0.15 = 0.02kg