... in physics, biology or chemistry.18 selected physics, 32 selected biology, and 25 selected chemistry. Of these 16 chose both biology and chemistry, but only 7 chose both physics and chemistry and only 8 selected both phys and biology. Just 3 selected to take all three courses
Answers (1)
I'd solve this with a Venn diagram. I've drawn you one:
You know 3 people did all three subjects. You know 16 did biology and chemistry. Take off the three that did all three subjects and you've got the segment of people who did biology and chemistry (but not physics). Then do the same for the other overlaps. You'll end up with the image I drew for you.
Now you want to work out the figure in the red, blue and green sections (the students who only did one science). Again, you can work it out. For chemistry, 20 (13+3+4) students did chemistry plus at least one other student. We know 25 in total did chemistry so how many only did chemistry? 5.
Using the same method, how many only did physics and only did biology? Six only did physics and eleven only did biology.
Add up all the segments (13 + 3 + 4 + 5 + 5 + 6 + 11). Total number of students doing science: 47