Two-fifths is equivalent to 40 percent. Dividing the numerator, 2, by the denominator, 5, yields a decimal value of 0.40. Decimal values can be converted to percentages by multiplying by 100, which means that 0.40 is equal to 40 percent.
There are many ways to convert a decimal into a fraction. While the easiest way is to convert the fraction into a decimal first, it usually requires a calculator. An alternative method is to multiply the fraction so that the denominator becomes 100. To do so, multiply the top and bottom by the same amount. In the case of 2 over 5, multiplying by 20 yields a new fraction of 40 over 100. Because a percentage is the part out of a whole, or 100 percent, the numerator of 40 of this new fraction is equal to the fraction as a percentage.
One final way of converting a fraction to a percentage is with simple algebra. Because the percentage is a part of 100, the fraction can be set to equal some number, x, over 100. In this case, 2 over 5 is equal to x over 100. The variable is isolated by multiplying 2 by 100, resulting in 200 over 5, or 40, which is equal to the percentage x.