What is the maximum possible number of different pairs of chairs in which Frank and Ruby could sit?
zuhalon December 4, 2019
Can someone explain the question.
How does answer C is possible on first question? Can someone explain please.
Reply
Benon December 4, 2019
Hi Zuhal, thanks for the question!
This game has a major inference that we can use to our advantage. If there are 4 boys seated in 7 chairs, and no two boys can sit beside each other, then the boys must be seated in chairs 1, 3, 5, and 7.
The rule regarding Ivan is a convoluted way of saying that I sits 5th. So far we have _ _ _ _ I _ _
S sits east of I, giving us: _ _ _ _ I S _
F and R are together. We don't know who is west or east of the other. This block cannot fit in 7 (evidently). F is a boy and can therefore only sit in 1 or 3.
Since R is attached to F, we get these following scenarios.
F R _ T I S _ (we placed T in 4 because it is the only remaining slot for a girl) - H and J are interchangeable in 3 and 7
_ R F T I S _ (again, T in 4 because it is the only remaining slot for a girl) - H and J are interchangeable in 1 and 7
_ T F R I S _ (T is placed in 2 because it is the last remaining slot for a girl) - H and J are interchangeable again in 1 and 7
These are the three possible combinations that F and R can occupy and that is how we get answer choice C.
I hope this helps. Please let me know if you have any other questions.