Looks like a related question to this one: Changing rate/price of a token in Crowdsale if you set the rate is 2, then you can use 0.5eth to buy one token.
buyAmount = msg.value * rate
Looks like a related question to this one: Changing rate/price of a token in Crowdsale if you set the rate is 2, then you can use 0.5eth to buy one token.
buyAmount = msg.value * rate