Pink Kangaroo Maths Challenge: Ria Bakes Six Raspberry Pies

Question

I have been doing some practice papers for an upcoming UKMT Maths Challenge. There's one question I can't seem to grasp. I'm not sure entirely sure where to start.

I'm open to any ideas. Thank you in advance!

Answer 1

It cannot be $D$ bcause this implies:

1. Pies 1,2,3 and 4 were baked
2. Kids run in and eat hottest which is 4 in this case, leaving 1,2,3
3. Pie 5 is baked
4. Kids run in and eat hottest which is 5 in this case, leaving 1,2,3
5. Pie 6 is baked
6. Kids run in and eat hottest which is 6 in this case, leaving 1,2,3
7. Kids run in again and eat hottest which is now pie 3 (not pie 2)

Answer 2

I know the question has already been answered, but I just want to add (as you asked in the comments) that the fastest way of approaching these kinds of questions is to guess and check.

Essentially you have to run through all of the answer choices and figure out which one is wrong. This is more efficient because trying to come up with a possibility in which this possibility cannot occur is much harder as there are lots of ways in which the kids cannot eat the pies and vice versa (ways in which they can eat the pies).

This, I believe, would be the most efficient strategy: work with what they give you.

Answer 3

Another point to note is that a possible solution must have two consecutive numbers together at any point, D is the only one which does not (i.e. goes from 3 to 1 at the end of the sequence) so you know it cannot be D.