What is the maximum possible number of different pairs of chairs in which Frank and Ruby could sit?

zuhal on December 4, 2019

Can someone explain the question.

How does answer C is possible on first question? Can someone explain please.

1 Reply

Ben on 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.