you should multiply 2 at a time and not try to do them at the same time also if the fraction numbers a high you can cross simplify the numbers so multiplying them won't be as hard. so, for example, 8/12*16/36*50/100 you can simplify 8/12 to 2/3 16/36 to 4/9 50/100 to 1/2 then you can multiply 2/3*4/9 and then 8/27*1/2 to equal 8/54 and you can still simplify 8/54 to 4/27