A strip of paper is 9/10 inchrs long. Need to cut into 3/12 inch pieces. How many pieces will i be able to cut?

Finding a common denominator between 10 and 12 to be 10*12=120, we can multiply 9/10 by 12/12 and 3/12 by 10/10 to get 108/120 and 30/120 respectively. Dividing the 2 (as we want to know how much 3/12 or 30/120 goes into 9/10 or 108/120), we get

(108/120) / (30/120) = (108/120) * (120/30) = (108/30) = 3+18/30 (as 30 goes into 90 3 times and 108-90=18)