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The Number 28 Trivia Quiz

These are mathematical properties about the number 28.

A multiple-choice quiz by hotdogPi. Estimated time: 3 mins.

Author
hotdogPi

Time
3 mins

Type
Multiple Choice

Quiz #
353,618

Updated
Dec 03 21

# Qns
10

Difficulty
Average

Avg Score
7 / 10

Plays
380

One at a Time - Single Page - Timed Game

Question 1 of 10

1. What is the prime factorization of 28? Hint

2x2x5

2x2x7

2x3x7

2x3x5

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Question 2 of 10

2. Why is 28 a triangular number? Hint

It's the sum of integers from 1 to 7

It's the square root of 784

It's 3 cubed plus 1

2 is a factor of 8

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Question 3 of 10

3. True or false: 28 is a perfect number.

True

False

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Question 4 of 10

4. 28 is a sum of two cubes. Which ones? Hint

16 and 12

14 and 14

27 and 8

27 and 1

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Question 5 of 10

5. What is 28 in binary? Hint

11100

11000

11011

10110

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Question 6 of 10

6. True or false: 28 is in the Fibonacci sequence.

True

False

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Question 7 of 10

7. What is 28 squared? Hint

576

684

676

784

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Question 8 of 10

8. What is 28 in hexadecimal? Hint

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Question 9 of 10

9. How many unique integer factors does 28 have? Hint

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Question 10 of 10

10. What is the lowest square number divisible by 28? Hint

144

168

196

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Quiz Answer Key and Fun Facts

1. What is the prime factorization of 28?

Answer: 2x2x7

The prime factorization of a number tells what prime numbers multiply to that number. 2x2x5 is 20, 2x3x5 is 30, and 2x3x7 is 42.

2. Why is 28 a triangular number?

Answer: It's the sum of integers from 1 to 7

Each triangular number is the sum of all the integers between 1 and another positive integer. The list of triangular numbers begins with 1, 3, 6, 10, 15, 21, 28, 36, 45, and 55.

3. True or false: 28 is a perfect number.

Answer: True

28 is a perfect number because its factors (except for itself) are 1, 2, 4, 7, and 14, and they add up to 28, the number itself.

4. 28 is a sum of two cubes. Which ones?

Answer: 27 and 1

The first numbers that are a sum of any two cubes are 1, 2, 8, 9, 16, 27, 28, 35, and 56. This assumes that 0 is a cube because it is 0^3.

5. What is 28 in binary?

Answer: 11100

"11100" means 16+8+4. "11111" means 16+8+4+2+1. "10101" means 16+4+1. So, the incorrect choices were 27 (11011), 24 (11000), and 21 (10110).

6. True or false: 28 is in the Fibonacci sequence.

Answer: False

The Fibonacci sequence starts with 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89. You add the last two numbers to get to the current one. The sequence goes from 21 (8+13) to 34 (13+21), skipping over 28.

7. What is 28 squared?

Answer: 784

28 cubed is 21952. 28 to the fourth power is 614656.

8. What is 28 in hexadecimal?

Answer: 1c

Hexadecimal is base 16. It uses 0 through 9 and the letters a through f as digits. A is 10, b is 11, c is 12, d is 13, e is 14, and f is 15. Instead of there being a tens place and a ones place, there is a sixteens place and a ones place. So "1c" means 16 plus 12. "2a" would be 32 plus 10, which is 42.

9. How many unique integer factors does 28 have?

Answer: 6

Its six factors are 1, 2, 4, 7, 14, and 28. Only a square number can have an odd number of unique factors.

10. What is the lowest square number divisible by 28?

Answer: 196

196 is 28 times 7, and is also equal to 14 squared.

Source: Author hotdogPi

This quiz was reviewed by FunTrivia editor CellarDoor before going online.
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