Lesson Plan Week 5

Question 1

Nine dots are arranged in a three by three square. Connect each of the nine dots using only four straight lines and without lifting your pen from the paper.
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Question 2

You're a cook in a restaurant in a quaint country where clocks are outlawed. You have a four minute hourglass, a seven minute hourglass, and a pot of boiling water. A regular customer orders a nine-minute egg, and you know this person to be extremely picky and will not like it if you overcook or undercook the egg, even by a few seconds. What is the least amount of time it will take to prepare the egg, and how will you do it?

Question 3

Write the numbers 1, 2, 3, 4, 5, 6, 7, 8, and 9 into the circles so that the sums of the numbers on every segment are the same, and that this sum is the greatest possible.

Question 4

You must cut a birthday cake into exactly eight pieces, but you're only allowed to make three straight cuts, and you can't move pieces of the cake as you cut. How can you do it?

Question 5

Using the least amount of brackets in the following expression, can you get 6 as a result of the operations?

1 / 2 / 3 / 4

(If they get this one give:

Place brackets in the following expression, so that its value is 28.)

Question6

Calculator Work

  • Take a three-digit number, say 417.
  • Reverse the digits and subtract whichever number is the smaller from the bigger:
  • 714 − 417 = 297
  • Reverse the digits of the answer and add to the previous answer:
  • 792 + 297 = 1089
  • Try this process for other three-digit numbers. Do you always get 1089? Which numbers does it not work for?
  • What if you start with a four-digit or a two-digit number?

Question 7

You are on a game show. You are shown three closed doors. A prize is hidden behind one, and the game show host knows where it is. You are asked to select a door. You do. Before you open it, the host opens one of the other doors, showing that it is empty, then asks you if you'd like to change your guess. Should you, should you not, or doesn't it matter?

Question 8

Mr. Slow, Mr. Medium, Mr. Fast, and Mr. Speed must cross a rickety rope bridge in 17 minutes. The bridge can carry at most two people at a time. Furthermore, it's dark, and there is only one flashlight; any single person or pair of people crossing the bridge must have the flashlight with them. (The bridge is too wide for the flashlight to be thrown; it must be carried across.)

Each man walks at a different speed. A pair travelling together must walk at the rate of the slower man. Mr. Slow can cross the bridge in at most 10 minutes; Mr. Medium can cross in 5 minutes; Mr. Fast can cross in 2 minutes; Mr. Speed can cross in 1 minute. How do all four men get across in the bridge in 17 minutes?

Question 9

(Predictor cards on separate attachment)

Question 10

Utilities puzzle:

Connect water, gas and electricity to all houses without crossing lines:

Solution:

Impossible