10 coins have a mass of 45 grams. How many grams is one coin?

We can't tell from the information given. We don't know how many

different types of coins there are. All we know is that all 10 of them

on the scale at the same time have 45 grams of mass.

IF all the coins happen to be identical ... AND each one is worn down

the same amount, AND each one has the same amount of dirt and oil

on it ... then each one has (45/10) = 4.5 grams of mass.

But those are some big IFs.

45 / 10 = 4.5

There are 4.5 grams in each coin.