Round off improper fractions and divide the denominator into the numerator. An improper fraction is a fraction that has a numerator (top number) that's larger than the denominator (bottom number). Consider the example 34/11. Round 34 to 35 and 11 to 10. Then divide 35 by 10. You know that 10 goes into 35 three times with 5 left over. Therefore, you could estimate the mixed fraction 3 5/10, which is simplified to 3 1/2.
Write numbers to the left of a decimal as the whole number in a mixed fraction. For example, if you have 4.752, you would write the 4 as the whole number.
Round off numbers to the right of the decimal and place them over a multiple of 10. If you're rounding to one digit past the decimal, you would use 10 as the denominator. Add a zero for each additional number to the right of the decimal. For example, if you have 4.752, round .752 to .75. Since there are two digits to the right of the decimal, place the 75 over 100. In this case, your estimation would be 4 75/100, which simplifies to 4 3/4.