[Video] Q16: The table above shows the observed mating frequencies among a group of fruit flies raised on either a starch medium or a maltose medium. what fraction of the observed mating were between fruit flies that were raised on the same medium?

Explanation for Question 16 From the Math (Calc) Section on the 2019 March Sat

Question 16 says the table above shows the observed meeting frequencies, 2 Amani group of fruit flies raised on either a starch medium or a Malthouse 3 medium. What fraction of the observed meetings were between fruit flies that were raised 4 on the same media. So we need to figure out what this fraction is. 5 The denominator is going to be the total group that we're pulling from. 6 And here that's all of the observed meetings. 7 So we know that that's just all of the meetings, 8 right? And that total is 59 right here on the table. 9 So our denominator is 59. And from that, 10 we can automatically eliminate a because it has the wrong denominator. 11 Next we're trying to find what amount of fruit flies were raised on the 12 same medium. So the find that we need to add together, 13 the amount that were both raised on starch, 14 which is 22 and the amount that were both raised on Mount toast, 15 which is 20. So all we have to do is add 20 and 22, 16 which gives us 42. And that is our numerator, 17 which means that the answer must be D 42 over 59.