In order to change 3.4 into a mixed number of a fraction is by turning it into a fraction first. 3.4 is the same as saying 3 and 2/5 ( 3 2/5 ). Now, you need to multiply your whole number (3) and denominator (5) , which will give you 15. Add 15 to your numerator (2) and you will get 17. Place 17 over you original denominator (5). Your answer will be 13/5. (;