What property of matter are you measuring if you are using a triple beam balance?

A triple beam balance measures 'mass'(a property of matter) in gram.

Explanation:

Properties of matter are measurable traits like colour, mass, length, breadth, odour, density, temperature, malleability, melting point etc. Triple beam balance is an instrument used to measure mass of an object (mass of an object is the amount of matter contained in the object).

It is called triple beam balance because it has three beams that allow one to move objects of known masses along the beam. It measures mass precisely. The instrument had reading error of +/- 0.05grams. It contain three beams. The front beam is the smallest, the middle beam has the largest size while the end beam is the medium beam size.

there are two significant figures.

considering the question as per the attachment

here we can see that the radon nuclide has 222 as the atomic mass number and 86 as the atomic number.

when it undergoes nuclear fission it gives polonium which has atomic mass number as 218 and atomic number will be 84 along with a helium nucleus which has 4 atomic mass number and 2 as its atomic number.

222 = 218 + 4 (atomic mass number)

86 = ? + 2; therefore ? = 86-2 = 84.

the atomic mass number of polonium will be 84.