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A pharmaceutical company has tested five drugs on three different organisms. The following incomplete table reports if a drug works on the given organism. For example, drug A works on organism R while B and C work on Q.

DrugOrganism POrganism QOrganism R
A✔
B✔
C✔
D
E

Following additional information is available:

  • Each drug works on at least one organism but not more than two organisms.
  • Each organism can be treated with at least two and at most three of these five drugs.
  • On whichever organism A works, B also works. Similarly, on whichever organism C works. D also works.
  • D and E do not work on the same organism.

Drug E works on

Solution

✅ Correct Option: 4
Slide 1/6
DrugOrganism POrganism QOrganism R
A✔
B✔✔
C✔
D
E

If drug A works on an organism, drug B will also work on the same organism:

DrugOrganism POrganism QOrganism R
A✔
B✔✔
C✔
D✔
E

If drug C works on an organism, drug D will also work on the same organism:

DrugOrganism POrganism QOrganism 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.

DrugOrganism POrganism QOrganism 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.

DrugOrganism POrganism QOrganism 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.

DrugOrganism POrganism QOrganism 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.

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