We are told that for the recycling drive, there is a 2:5 ratio. It means that for every two glass bottles collected, they collected five plastic bottles. That means that seven (taking two glass bottles and adding five plastic bottles) of *both* kinds were collected. So we can say that the ratio of glass bottles to all bottles is 2:7.
That 2:7 ratio is what we use. We make a proportion with that 2:7 ratio on the left, the totals on the right, the amount of glass bottles on the top, the amount of all kinds of bottles on the bottle.
[tex] \frac{2}{7} = \frac{?}{476} [/tex]
We could fill in the 2, 7, and the total. We don't know the amount of glass bottles. Let that be B.
[tex] \frac{2}{7} = \frac{B}{476} [/tex]
To find B, we cross multiply and solve for B.
7B = 952 cross multiplying 7 and B, 2 and 476
B = 136 divide both sides by 7
Thus there 136 glass bottles - - choice B - - collected.
