Discuss all possibilities
Like human viruses, computer viruses come in different forms and can affect your computer in many ways. Computer viruses are small software programs that are designed to spread from one computer to another and to interfere with computer operation. Assume that you have 60 computers in your laboratory. Some of these computers are infected with either . When you select any 41 computers, there will be always different computers infected with these three type of viruses. How many could be in the laboratory?
Report your answer as the number of the computers infected with ?
The answer is 20.
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1 solution
Out of the 6 0 computers, assume that there are:
F : : computers virus free,
B : : infected with Boot Virus,
C : : infected with Companion Virus, and
M : : infected with a Macro virus.
with B ≥ C ≥ M (assumptions).
To make sure that among the 4 1 computers there is one infected with Macro Virus, we can say that F + C + B ≤ 4 0 .
Then the estimated number of Macro Viruses M must be ≥ 2 0 (at least) which ⟹ B = C = M = 2 0 .