3/8 expressed as a percentage is '42.1 . To do this by yourself, just pull out a calculator, divide the numerator by the denominator, and multiply the number you got by 100. You'll have your percent.
You can also enter '3/8*100=' into google too,just to make it easier.
here's a better answer:
if 1/4 is 25%, then 1/8 is half that number, or 12.5%. But, we don't want one eighth, we want three of them. 3 times 12.5 is 37.5. So 3/8 = 37.5%.