The ratio of green pens to black pens in a box is two to seven. What fraction of the total number of pens are green? Circle your answer. The options are half, two-sevenths, two-ninths, and seven-ninths.
The first thing we need to do when we’re looking at a ratio is look at the order. We’re told that the ratio of green pens to black pens in a box is two to seven. So therefore, as green comes first, that’s gonna correspond to the two, so two
parts. And then we have black. So that’s gonna correspond to seven, so seven parts.
So then what we know is that there are two parts which are green pens, seven parts
which are black pens. And what we want to know is what are the total number of parts. So to find this out, we add two and seven, which is going to be nine. So we know that there are nine parts in total.
So now what we want to do is find out the fraction of the total number of pens that
are green. Well, we know that the total number of parts is nine. And two of those nine parts are green. So therefore, we can say that green is equal to two-ninths of the total number of
pens. And we get that because two parts are green. And that’s our numerator. And then our denominator is the total parts, which is nine.
So we can circle the correct answer, which is the third answer, two-ninths, because
two-ninths is the fraction of total number of pens that are green.