Computational Thinking Quiz- F

Gaby’s dad gives her four boxes containing four different gifts; a bracelet, a notebook, a ring, and

perfume. There is only one gift per box.

By applying logic, Gaby can keep the one she likes the most.

Each box has a label that does not lie.

Question

Gaby wants to keep the ring. Which box has the ring in it?

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Answer explanation

We know for a fact that labels don’t lie, so the bracelet and the notebook must be in either box A

or B. Either the notebook is in box A and the bracelet is in box B or vice versa. That leaves Gaby with

box C and box D. From the previous statement, we know that the bracelet is either in box A or box B,

meaning it cannot be in box D. Therefore the ring must be in box D, which is what Gaby should choose.

For completeness, we now also know that the perfume is in box C.

A stone-sorting factory has two kinds of machines. Each machine will remove some of the stones

and return the others as its output.

The pink machine is called an “odd machine”. It removes every second stone just like the

picture below:

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Answer explanation

Beavers love to play a game called “Strawberry Hunt”! These are the game rules:

1. A different number of strawberries are placed on each area of a field.

2. A player starts from any area of the field and eats the strawberries in that area.

3. A player then can take only 3 total steps. Each step can be:

• Move up one area

• Move down one area

• Move right one area

• Move left one area

4. After each step, eat all the strawberries found in that area of the field.

Question

How many strawberries can Alessa eat at most?

• 32

• 23

• 24

• 42

Answer explanation

Lulu is learning to write programs that change the colour of images. She wants to turn her frog green.

She has written four different programs for changing the colour of the frog. Each program consists of

a sequence of ‘if-then-else’ or ‘if-then’ statements. Each of the steps are carried out in order, one after

the other. Each step will change a frog’s colour once.

For example, for the following instruction:

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Answer explanation

During their vacation in Ohrid, Monika and

Veronika bought Ohrid pearls and made

necklaces from them. Their necklaces are

shown below.

They decided to change the pearls in their necklaces using the following steps.

1. Monika and Veronika each take a pearl from the right of their own necklace.

2. If the pearl is pink (square) or orange (triangle) they add it to the left of the other’s necklace.

If it is one of the other colours, they add it to the left of their own necklace. Monika goes first

and then Veronika.

3. If each has given three pearls to the other, they stop, otherwise they go to step 1.

Question

What do Monika’s and Veronika’s necklaces look like after the steps have been completed?

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Answer explanation

Tic-tac-toe is a paper-and-pencil game for two players.

Rules:

• Players choose who uses X as their mark and who uses O.

• One player starts, then both players take turns marking the spaces in a three-by-three grid with an

X or an O.

• The player who succeeds in placing three of their marks in a horizontal, vertical, or diagonal row is

the winner.

• If no one succeeds and all nine boxes are filled, the game ends in a draw.

Example:

The following images show the first two moves each player made, and the last move they made in

a game. (The moves made on each turn are highlighted.)

The image on the right, is what we call the ‘result sheet’ of a completed game. Not all sheets, that are

filled randomly with X or O, are valid result sheets according to the rules above.

Question

Which of the following images is the only valid result sheet, of a completed game, according to the

rules above?

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Answer explanation

The picture shows several windmills and the roads connecting them to the storage shed. Every evening,

the windmills produce sacks of flour and place them out the front.

Willie the beaver is supposed to pick up all the sacks and bring them to the storage shed before sunset.

Willie can carry several sacks at the same time, but the total weight cannot be heavier than 15kg.

The time it takes Willie to travel from one windmill to another and to the storage shed is shown in

the picture.

Question

Starting from the storage shed, Willie the beaver wants to bring in all the sacks to the storage

shed as fast as possible. How many minutes does it take him to carry out this task?

• 50 minutes

• 31 minutes

• 44 minutes

• 54 minutes

Answer explanation

In a land called Mysteria, there lives a wizard.

The wizard can transform into a fairy, or create a fairy to their right.

The fairy can transform into a potion with a dragon on its right, or transform into a wizard with a

potion on their left and a dragon on their right.

These magical transformations can happen any number of times, in any order. That is, any wizard and

any fairy can transform at any time. In this way a long arrangement of magical things can be created

from a single wizard or fairy.

Question

Starting with a single wizard, which arrangement is not possible to obtain?

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Answer explanation

A jungle community, living on six islands, wants

to connect these islands by building a network of

canopy bridges.

A plan of all possible bridges was created. The

numbers show the cost to build each bridge, for each

possible connection. The bridges do not intersect

with each other.

The community wants to link all the islands so that

it is possible to travel from any island to any other

island. Travel between islands can either be done

directly, or by going indirectly through one or more

islands.

At the same time, the community wants to build the

bridges as cheap as possible.

Question

What is the cheapest whole number that can be spent to link up all six islands?

• 44

• 24

• 40

• 46

Answer explanation

April and Sandy challenged each other to a number game, but they both got different results!

They are trying to form a six-digit number, using each of these digits exactly once:

\(1, 2, 3, 4, 5, 6\).

The number must be the smallest number that satisfies all these conditions:

\[4 \to 1, 1 \to 2, 4 \to 5, 2 \to 3, 5 \to 2, 3 \to 6\]

Condition \(a \to b\) means that, in the number, digit \(a\) must be to the left of digit \(b\).

Question:

What is the smallest number that meets all of these conditions?

• 4 2 5 1 3 6

• 4 1 5 2 3 6

• 4 1 5 3 2 6

• 4 3 5 2 1 6

Answer explanation

Explanation:

This number satisfies all conditions, and it is the smallest such number.

The number 4 5 1 2 3 6 also satisfies all conditions, but it is not the smallest such number, because it is

larger than 4 1 5 2 3 6.

Here is one way to reach the final number: we consider each condition one by one, and write the

relevant digits into a sequence, which satisfies all conditions considered so far. If it is unclear where to

put a new digit, we can write it onto a separate line.