CyberChallenge.IT 2020

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CyberChallenge.IT 2020 - Pretest

Demo of the pretest for the 2020 edition of CyberChallenge.IT

Additional material for other tests is available at the link https://cyberchallenge.it/training

Question 1

Consider a two-pan balance scale. There are 32 tennis balls. 31 of them have the same weight and the thirty-second is a bit heavier.

In the worst case scenario, what is the minimum number of weighings you need to identify the heavy one?

1 point

Clear selection

Question 2

Only one of the following sentences is true.

- Alice: “Bob is the tallest”

- Bob: “Charlie is the tallest”

- Charlie: “I’m not the tallest”

- David: “I’m not the tallest”

How many cards will receive the oldest child?

1 point

David

Bob

Alice

Charlie

Clear selection

Question 3

Given 100 balls in a box, numbered from 1 to 100:

What is the probability of extracting a perfect cube number?

1 point

1/25

4/50

1/20

1/24

Clear selection

Question 4

Consider 3 different programmers:

- Alice can finish a project in 1 hour

- Bob can finish a project in 2 hours

- Charlie can finish a project in 6 hours

How long would they take to complete a project?

1 point

36 minutes

30 minutes

24 minutes

42 minutes

Clear selection

Question 5

Given the even numbers between 2 and 2020:

How many numbers are not divisible by 5 or 7?

1 point

866

1384

808

692

Clear selection

Question 6

Infinite coins of 1, 2 and 5 cents are available.

How many different ways we can make 7 cents?

1 point

Clear selection

Question 7

Consider a fruit basket.

- All fruits except 3 are apples

- All fruits except 4 are oranges

- All fruits except 1 are bananas

How many fruits are there in total?

1 point

Clear selection

Question 8

John has 1260 candies. He wants to give them in equal number to each of his friends, that are less than 100.

How many friends has John at most?

1 point

Clear selection

Question 9

What is the greatest positive integer n such that the arithmetic mean of the numbers from 1 to n is less than 2020?

1 point

2020

4038

4040

4039

Clear selection

Question 10

Consider the following incomplete function which sorts three numbers:

Which of the following conditions for $1, $2, $3, $4 and $5 makes the program correct?

1 point

(a < b), (b < c), (a < c), (a < c), (b < c)

(a < b), (a < c), (b > c), (a < c), (b < c)

(a < b), (b < c), (a < c), (b < c), (a < c)

(a < b), (a < c), (b < c), (c > a), (b < c)

Clear selection

Question 11

Consider the following function that accept an unsigned integer number greater than two:

What does the function return?

1 point

true if n is prime, false otherwise

false if n is prime, true otherwise

false if k < n, true otherwise

true if n=k*k, false otherwise

Clear selection

Question 12

Consider a function that checks if a vector V of size N is palindrome:

Which of the following code fragments for $1 and $2 makes the program more correct?

1 point

N/2 and (V[i] != V[N-i-1])

N and (V[i] != V[N-i])

N-1 and (V[i] != V[N-i-1])

N/2 and (V[i] != V[N-i])

Clear selection

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