Aptitude

Question

. Once Jay, Mira and Om went for trekking. Every one of them saw a bird that other two did not see and each pair saw one bird that the third did not. There was one bird which was seen by all three of them. Of the birds Jay saw, two were blue. Of the birds Mira saw, three were blue. Of the birds Om saw, four were blue. How many blue and non-blue birds were seen in all? Your answer

Anonymous · Accepted Answer

Blue Jay · Answer

There were seven birds, five of which were blue, and two were not.

Let's name the birds according to who saw them.

Three were seen by only one person: J, M, and O.

Three were seen by two people: JM, JO, and MO.

One was seen by all three: JMO.

Four birds seen by Om were blue. Om saw four birds in total, O, JO, MO, and JMO, so all of these were blue.

Two blue birds were seen by Jay, and we know that JO and JMO were blue, so these were Jay's two blue birds, and his other two, J and JM, were non-blue.

Mira saw three blue birds, and we know that MO and JMO were blue and JM was not, so her other bird, M, must be the third blue one she saw.

This gives us five blue birds, M, O, JO, MO, and JMO, and two non-blue, J and JM.

Aptitude

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