Solution
| Drug | Organism P | Organism Q | Organism R |
|---|---|---|---|
| A | ✔ | ||
| B | ✔ | ✔ | |
| C | ✔ | ||
| D | |||
| E |
If drug A works on an organism, drug B will also work on the same organism:
| Drug | Organism P | Organism Q | Organism R |
|---|---|---|---|
| A | ✔ | ||
| B | ✔ | ✔ | |
| C | ✔ | ||
| D | ✔ | ||
| E |
If drug C works on an organism, drug D will also work on the same organism:
| Drug | Organism P | Organism Q | Organism R |
|---|---|---|---|
| A | × | ✔ | |
| B | × | ✔ | ✔ |
| C | ✔ | ||
| D | ✔ | ||
| E | × |
An organism can be treated by 2 or 3 drugs only.
A drug can work on 1 or 2 organisms only.
| Drug | Organism P | Organism Q | Organism R |
|---|---|---|---|
| A | × | × | ✔ |
| B | × | ✔ | ✔ |
| C | ✔ | ||
| D | ✔ | ||
| E | × |
Now, we cannot put a checkmark on A for P, because B will also have to work in that case, but we have established it can't.
| Drug | Organism P | Organism Q | Organism R |
|---|---|---|---|
| A | × | × | ✔ |
| B | × | ✔ | ✔ |
| C | ✔ | ✔ | |
| D | ✔ | ✔ | |
| E | × | × |
If we put a checkmark on E, then D won't work, which will only leave us with C, but atleast 2 drugs work on an organism. Hence, it'll have to be C and D for P. It also satisfies the given condition that what C works on, D works on as well.
| Drug | Organism P | Organism Q | Organism R |
|---|---|---|---|
| A | × | × | ✔ |
| B | × | ✔ | ✔ |
| C | ✔ | ✔ | × |
| D | ✔ | ✔ | × |
| E | × | × | ✔ |
We know that E will have to work on atleast one organism, and only R is remaining, so we'll put a checkmark on that. Now R has 3 drugs working on it, which means no more drugs can work on it, hence we'll cancel out the rest.
We see that E works on only R.
More from this set:
Question 27
Question 29
Question 30