I've got the home instructors guide, and it shows two different ways to solve the problem. I don't understand why 6 units equals 48. Where did the six units come from?
Why did the book multiply the fraction of the left over part of the red and yellow beads to get 10 units instead of subtracting the red and yellow beads from the whole?
And if we change the units to 20 then the red beads are 5/20 and the yellow beads are 12/20. I subtract those from 20/20 to get 3/20. So 3/20 equals the blue beads. 1/20 equals 16, and the total beads are 320. But, that's not what the book says.