Um... Three one eighth teaspoons do not equal a three fourth teaspoon. Think about it. Three one eighth teaspoons equal three-eighths and three-eighths are not equivalent to a three fourth teaspoon.
no one fourth AND one fourth teaspoon equals 1/2 teaspoon one half of one fourth equals 1/8 teaspoon
Again this is an answer from the UK. We normally say that 5mls is one teaspoon. Therefore we would answer your question that 1ml is 1/5th of a teaspoon.
A fourth of a half is an eighth, a half of a fourth is still an eighth. They're both equal.
No, it equals one eighth.