University of Waterloo Logo and CEMC Banner

2023 Beaver Computing Challenge
(Grade 7 & 8)

Questions

Part A

Lakes

Story

Six lakes are connected by rivers. Water always flows from a lake with a greater height above sea level to a lake with a lesser height above sea level.

An online search provides the following information about these lakes:

Lake pH Level Height Above Sea Level (m) Estimated Fish Population
Atlyn 6.5 320 32000
Clare 7.1 740 1500
Doffin 6.8 490 65000
Kazba 7.2 673 4200
Mus 6.5 973 22100
Soul 6.2 382 43000

Question

In what order does water flow between these six lakes?

  1. Atlyn, Clare, Doffin, Kazba, Mus, Soul
  2. Mus, Clare, Soul, Atlyn, Doffin, Kazba
  3. Kazba, Clare, Doffin, Mus, Atlyn, Soul
  4. Mus, Clare, Kazba, Doffin, Soul, Atlyn

Ogham Code

Story

Ogham is a medieval alphabet used to write words vertically along a pillar.

Each letter is represented by a group of lines that always touches or crosses the pillar in the same way. Groups (letters) are separated by big gaps and arranged upwards from the bottom of the pillar to the top of the pillar.

Eabha writes four words using the Ogham alphabet as shown. The words are BANANAS, BERRIES, LETTUCE, and ORANGES, but we do not know which word corresponds to which image.

A description of the diagram follows.

Question

From left to right, what is the order in which Eabha has written these words?

  1. LETTUCE, ORANGES, BANANAS, BERRIES
  2. ORANGES, LETTUCE, BANANAS, BERRIES
  3. BERRIES, BANANAS, LETTUCE, ORANGES
  4. LETTUCE, ORANGES, BERRIES, BANANAS

Flower Shop

Story

A florist makes bouquets by following these three steps in order:

  1. Pick one flower from the bucket shown on the left to start the bouquet.

  2. If the flower picked is a daisy , add a second daisy to the bouquet.

  3. Complete the bouquet by adding at least one branch of leaves from the bucket shown on the right.

The bucket on the left has two roses and two daisies. The bucket on the right has three branches of leaves.

Question

Which bouquet might the florist make?


  1. One daisy and two branches of leaves.

  2. Two roses and one branch of leaves.

  3. Two daisies and one branch of leaves.

  4. One daisy, one rose, and one branch of leaves.

Magic Tree

Story

Bain the Beaver has a magical tree growing near their home.

Whenever a bird lands on it, the tree sprouts 2 apples.

Whenever a squirrel climbs up it, the tree drops 1 apple (if it has any).

Bain has also noticed that whenever a snake visits the tree, all of the apples instantly disappear!

One morning Bain notes that the magical tree contains 25 apples. Bain then spends the rest of the day drawing pictures of all the animals that come to the tree. The drawings, in order, are:

birdbird squirrelbirdsnake squirrel squirrelbirdbirdbird squirrelbirdsnakebirdbirdbirdbird squirrel

Question

How many apples are on the tree at the end of the day?

  1. 3
  2. 7
  3. 17
  4. 31

Equipment Sorting

Story

An equipment tube contains basketballs

Sarah reorganizes the equipment by moving the balls one by one. That is, Sarah takes each ball out of the top of the equipment tube and then drops it into the top of one of the smaller tubes. After moving each ball once, each type of ball is stored together in a smaller tube.

The three smaller tubes are empty. The equipment tube has 3 basketballs, 3 soccer balls, and 3 volleyballs in a stack. The order of the balls in the stack, from top to bottom, is basketball, soccer ball, volleyball, soccer ball, basketball, volleyball, volleyball, soccer ball, basketball.

All the balls are the same size and each smaller tube holds three balls.

Question

Which of the following statements is true?

  1. Sarah fills the tube of soccer balls first.
  2. Sarah fills the tube of volleyballs last.
  3. Sarah fills the tube of soccer balls after filling the tube of basketballs.
  4. Sarah fills the tube of volleyballs before filling the tube of basketballs.

Part B

Levers

Story

Jacinta’s new helicopter has a control panel with four levers that each control a different system.

The labels on the levers are missing, and Jacinta was told that the system was wired in a confusing way so she doesn’t know which lever controls which system. All she knows is that putting a lever up turns one system and its indicator light on, and putting a lever down turns one system and its indicator light off.

The image shows which indicator lights are on for three different configurations of the levers.

The first configuration has levers 1 and 3 down and levers 2 and 4 up. In this case, the indicator lights for the heating and ventilation systems are on and the other two lights are off. The second configuration has levers 1, 2, and 4 up, and lever 3 down. In this case, the indicator lights for the heating, ventilation, and humidity systems are on and the other light is off. The third configuration has levers 1, 3, and 4 up, and lever 2 down. In this case, the indicator lights for the ventilation, lights, and humidity systems are on and the other light is off.

Question

Which of the following correctly matches each lever to the system that it controls?

  1. 1: heat. 2: ventilation. 3: lights. 4: humidity.
  2. 1: humidity. 2: ventilation. 3: lights. 4: heat.
  3. 1: humidity. 2: heat. 3: lights. 4: ventilation.
  4. 1: ventilation. 2: heat. 3: lights. 4: humidity.

Vending Machine

Story

In Beaverland, paper money comes in four different values: 10, 20, 50, and 100. These values are written on the paper money and they are also encoded using a grid of nine squares that are either blank or filled in, as shown.

A description of the diagram follows.

When paper money is inserted into a vending machine, the machine scans all nine grid squares and determines whether each square is blank or filled in. This is how the vending machine identifies the value of the paper money. For example, if the vending machine determines that only the squares in the rightmost column are filled in, it identifies the paper money as having a value of 100.

Sylvia has noticed that the vending machine doesn’t need to scan all nine squares. It could correctly identify the value of the paper money by scanning only two squares.

Question

Which two squares could Sylvia reprogram the vending machine to scan (ignoring all others) in order to identify the value of the paper money?


  1. The leftmost square in the middle row and the rightmost square in the middle row.

  2. The leftmost square in the bottom row and the middle square in the bottom row.

  3. The rightmost square in the top row and the leftmost square in the bottom row.

  4. The middle square in the middle row and the middle square in the bottom row.

Restoring Music

Story

Juno has found an ancient diagram that describes how to compose pieces of music using just five types of notes. Any note can be selected as the first note, but a note can only be selected next if there is an arrow pointing to it from the previous note.

A description of the diagram follows.

Juno has also found the sheet containing a piece of music which was composed using the diagram above. Two notes are missing due to a hole torn in the sheet as shown below.