Question 30: People use a Robovan balance to measure the mass of a lock. When balanced, one finds a 100g weight on one pan and a 15g weight on the other. . The mass of the key is:

How to use a Robovan balance: Place the object to be weighed on the left pan, put a number of weights on the other side of the scale so that the lever is balanced, the needle is in the center of the scale. .

We have: When balancing, one sees a 100g weight on one pan and a 15g weight on the other plate.

⇒ 100g = mkhoa + 15g

mkhoa = 100 – 15 = 85g

The answer to choose is: EASY