Help me.

Apiece of metal with a length of 1.42 cm was measured using four different instruments. which of the following measurements is the most accurate?

Astudent reacts 13 moles of iron with 21 moles of oxygen according to the following equation:

A4.86 g piece of metal was placed in a graduated cylinder containing 15.5 ml of water. the water level rose to 17.3 ml. what is the density of the metal. i need the steps of how to solve it to so i can use a formula to work out other problems.