Why is a teacher's feedback valuable?

Because they could help you move on better with your strategy and ultimately get you better scores on tests  

Through feedback, teachers can provide the students with suggestions for development, learning strategies and corrections for errors. The importance of constructive feedback allows for many positive opportunities. This component also enhances a student's self-efficacy and provides an avenue for motivation.

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