How many coins are 100g?

Answer 1

It depends on the coin's weight.

For example a current US 1¢ coin weighs 2.5 gm so it would take 40 of them to weigh 100 gm (100/2.5 = 40)

But if you used a heavier coin, say a UK £1 coin that weighs 9.5 gm, you'd need far fewer of them to weigh 100 gm - in fact, only about 10 coins. (100/9.5 = 10.5 +/-)