Lesson 4: Remix Fund Me decimals issue

[anonfawkes73]

Hey guys, I've seen many questions regarding this part of the video but nobody is asking that, so I'm probably lost about something.

    function getConversionRate(uint256 ethAmount) public view returns (uint256) {
        uint256 ethPrice = getPrice();
        // 3000_000000000000000000 ETH/USD
        // 1_000000000000000000 ETH
        uint256 ethAmountInUSD = (ethPrice * ethAmount) / 1e18;
        return ethAmountInUSD;
        // 2 * 1e21 = 3000_000000000000000000
    }

I'm a bit lost on that part (around 4:20 on the video).

• getPrice(); is giving us a uint256 with 18 decimals, and that's ok.
• uint256 ethAmount doesn't have 18 explicit decimals, so I don't understand why he says that
• since that, uint256 ethAmountInUSD = (ethPrice * ethAmount) / 1e18 is giving us a rounded number without any decimals, why does he say that it is giving us a number with 21 decimals // 2 * 1e21 = 3000_000000000000000000 ?

and why after he multiplies uint256 public minimumUsd = 50 * **1e18**; // 1 * 10 ** 18

[AnkushMahajan1]

Hey Let me try to answer your doubts.

1. uint256 ethAmount takes value from actual value bar on remix ide so it is usually in wei regardless you choose gwei or eth. Hence 18 decimals.
2. Solidity doesnt have decimal system n at the time of recording the value of eth to usd was 3000 so convert that to wei gives us 3 *1e21 or 3000 * 1e18. so those 3 zero of conversion rate gets added as well hence 21 decimals.
3. uint256 public minimumUsd = 50 * 1e18; // This is one eth to wei rate 1 * 10 ** 18 . And in order to compare solidity uses in metrics of wei hence that multiplication to convert it to wei

Hope that answers your Question @anonfawkes73