# How many weighing Do you need to find the counterfeit coin among 81 coins?

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## How many weighing Do you need to find the counterfeit coin among 81 coins?

four weighings
It then takes only one more move to identify the light coin from within that lighter stack. So in two weighings, we can find a single light coin from a set of 3 × 3 = 9. By extension, it would take only three weighings to find the odd light coin among 27 coins, and four weighings to find it from 81 coins.

## What is the minimum number of weighings needed to identify the stack with the fake coins?

What is the minimum number of weighings needed to identify which stack contains the fake coins? Explain. Author’s hint: The answer is that one weighing is enough.

How can you tell a fake coin?

Counterfeit coins typically have casting seams, which can be very apparent to the naked eye. Fake coins often times will contain hole markings. Additionally, many coins have intricate designs or textures that are associated with that particular coin and its series.

### How can you tell if a coin is counterfeit?

Use a scale that is accurate to within 0.01 grams to measure the weight of the coin. Compare your results to that of the genuine coin. If they are significantly off, you may have a counterfeit coin. Use an extremely strong magnet to see if the coin is attracted to it.

### Are coins counterfeited?

Coin counterfeiting of valuable antique coins is common; modern high-value coins are also counterfeited and circulated. Counterfeit antique coins are generally made to a very high standard so that they can deceive experts. This is not easy and many coins still stand out.

How do you spot fake coins?

## Where do the coins go after they leave the bank?

The coins make their way back to the Federal Reserve Bank at some point because banks often accumulate more cash than they need for day-to-day transactions. They deposit the excess cash into their checking account at a local branch of the Federal Reserve Bank until their customers need it.

## How long do US coins stay in circulation?

Coins circulate from the Federal Reserve Bank to the private banks to you and back again until they are worn out, unfit for circulation. The Federal Reserve replaces those coins by ordering new ones from the U.S. Mint—and once those coins are minted, a new circulation cycle begins. A circulating coin generally lasts 30 years or longer.

How many coins does the US mint produce?

How many coins does the United States Mint produce and where are they made? In 2000, the U.S. Mint produced approximately 28 billion coins for general circulation. These are made in the Mint facilities in Philadelphia, PA and Denver, CO.

### Where does the United States get its coins from?

“The United States Mint ships its coins to Federal Reserve Banks, which are responsible for putting coins and paper money into circulation and also for withdrawing them from circulation when they are worn out. When a private bank needs coins to provide to you and its other customers, it purchases them from a Federal Reserve Bank.