  # Five Plus Two is What? Trivia Quiz

### Five plus two is obviously seven, but what other numbers can we make from five and two?

A multiple-choice quiz by AdamM7. Estimated time: 3 mins.

Author
Time
3 mins
Type
Multiple Choice
Quiz #
373,639
Updated
Dec 03 21
# Qns
10
Difficulty
Average
Avg Score
7 / 10
Plays
909
Last 3 plays: marianjoy (7/10), john62450 (7/10), jonathanw55 (2/10).
1. First, let's explore addition a bit more.
5+2 = 2+5 = 7
So, the order of the numbers doesn't matter with addition. What is this property called?
Hint

Commutative
Functional rearranging
Quotient

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2. Subtraction is another basic operation. Using five and two, you can get 3 or -3, depending on which number goes first. In 5−2 = 3, what is the 5 called? Hint

Vector
Difference
Minuend
Numerator

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3. Multiplication of five and two yields ten. What relation are five and two to ten? Hint

Its prime factors
Its lowest common multiple
Its interpunct
Its matrix

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4. Division is the opposite of multiplication: order matters, so using the numbers five and two we can make either 2.5 or 0.4 with division. Which of these signs cannot be used for division? Hint

Obelus
Vinculum
Forward slash
Co-ordinate parentheses

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5. Using this operation, we can get the numbers 25 or 32 from five and two. What is it? Hint

Calculus
Analysis
Exponentiation

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6. If five is the radicand and two is the degree, we can get a number roughly equal to 2.236. We can say 2.236 is the ___ of five. Hint

Reciprocal
Square root
Topological equivalent
Gambit

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7. The logarithm of 5 to base 2 is (roughly) 2.322. What does this mean? Hint

2^2.322 = 5
2.322^2 = 5
2 x 2.322 = 5
2 + 2.322 = 5

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8. 5 mod 2 is what? Hint

1
5
2
3

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9. Tetration is our next process. 5^^2 means 5 to the power of itself. What is 5^^2? Hint

100
3125
250,000
5500

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10. How is the decimal number 5 written in base 2 (binary)? Hint

221
e
05
101

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Quiz Answer Key and Fun Facts
1. First, let's explore addition a bit more. 5+2 = 2+5 = 7 So, the order of the numbers doesn't matter with addition. What is this property called?

Addition is commutative, as is multiplication. It is also associative, which means the order is irrelevant no matter how many numbers you add.

For instance, 2+5+25+52 = 52+25+5+2 = 5+52+2+25 etc.
2. Subtraction is another basic operation. Using five and two, you can get 3 or -3, depending on which number goes first. In 5−2 = 3, what is the 5 called?

In 5−2 = 3, the 5 is called a minuend, the 2 is a subtrahend and the 3 is the difference.

With subtraction of two numbers, the order does matter but changing the order just changes the sign (positive/negative) - their absolute values (distance from 0) are the same. For example, 52−25 = 27, but 25−52 = -27. These numbers (27 and -27) have the same "absolute value", which just means that ignoring the sign, they are both 27.
3. Multiplication of five and two yields ten. What relation are five and two to ten?

Factors are numbers which divide into a bigger number to give a whole number. 10 divided by 5 is 2, and 10 divided by 2 is 5, so 2 and 5 are both factors of 10.

Prime factors are just factors that are also prime numbers (numbers which have no further factors other than one and itself). For instance, the prime factorisation of 52 is 2x2x13 (2^2 x 13).
4. Division is the opposite of multiplication: order matters, so using the numbers five and two we can make either 2.5 or 0.4 with division. Which of these signs cannot be used for division?

Two divided by 5 is 0.4 while five divided by 2 is 2.5.

2/5 = 0.4 uses a forward slash to denote division. A "vinculum" is a line, with one number on top of one another, often used to represent fractions. An "obelus" is a line with a dot above and beneath it, which looks like this: �
5. Using this operation, we can get the numbers 25 or 32 from five and two. What is it?

Exponentiation uses "powers": the power is usually written as a superscript to the right of the base, but on computers the caret (^) symbol can be used.

5^2 ("five squared") = 5x5 = 25
2^5 ("two to the power of five") = 2x2x2x2x2 = 32

So exponentiation is repeated multiplication: a^b means "a multiplied by itself b times". If the power is two, we can call it "_ squared", and if it is three, we can call it "_ cubed". No other powers have their own name, and are said aloud as "_ to the power of _".
6. If five is the radicand and two is the degree, we can get a number roughly equal to 2.236. We can say 2.236 is the ___ of five.

Roots are an opposite of exponentiation: 2.236^2 = 5, so 2.236 is the square root of 5.

A radix symbol is used for a square root, but other roots need the degree number superscripted. As with exponentiation, only two and three have their own names: it goes "square root", "cube root", "fourth root" etc.

Using two and five, we can actually make three numbers via roots. The fifth root of 2 is 1.149. Square roots always have two answers: one positive and one negative. Therefore, the square root of 5 can be 2.236 or -2.236.
7. The logarithm of 5 to base 2 is (roughly) 2.322. What does this mean?

Logarithms is the other opposite of exponentiation. A logarithm yields the power of x that will make y.

So, if 2^5 = 32, then the logarithm of 32 to base 2 is 5.

Using 2 and 5 as the base/antilogarithm, we can get two answers: 2.322 or 0.431.
8. 5 mod 2 is what?

The modulo operation finds the remainder. If we were doing 5 divided by 2, we would get two and a remainder of 1. Another way of looking at this is that you repeatedly subtract 2 from 5, until you get to a number smaller than the modulo (two): 5−2 = 3; 3−2 = 1, so 1 is the answer.

2 mod 5 is simply 2, as 2 is already smaller than 5.

Time can be thought of in terms of modulo operations. If it is 22:00 on Monday, and we want to know what time it will be in 55 hours, the answer is (22+55) mod 24 (because 24 is the number of hours in a day). 77 mod 24 = 77−3(24) = 5, so it will be 05:00 on Thursday (Monday + 3 days).
9. Tetration is our next process. 5^^2 means 5 to the power of itself. What is 5^^2?

Tetration is repeated exponentiation, that is to say, if we have x^^2 (x to the tetrated two), that is equal to x^x (x to the power of x).

So 5^^2 = 5^5 = 5x5x5x5x5 = 3125. (You didn't need to work this out fully, as 3125 was the only option ending in "5", and 5 to the power of anything will always end in a 5).

Giving another example, 3^^3 = 3^(3^3) = 3^27 = 7,625,597,484,987. As you can see, tetration gets incredibly large very quickly.
10. How is the decimal number 5 written in base 2 (binary)?

We normally use a decimal (base 10) system, which means we have 10 single-digit numbers (0, 1, 2, 3 etc.) In binary, there are only 2 single-digit numbers: 0 and 1.

The last digit (the equivalent of base 10's units column) is worth 1, the second-to-last is worth 2, the anti-penultimate 4, the next 8 etc. If the value in that position is a "1", you add the value of the position. If not, the number doesn't change.

So, in a three-digit number, the digits are worth (from right-to-left) 1, 2 and 4. In "101", the 1 digits are in the 1 and 4 value positions - 1+4 = 5.

Computers use binary, because it is easy to transfer knowledge like this. A "1" can be represent by a pulse or a light or anything, and a "0" is no pulse/light etc. Although it needs more bits of information than decimal systems do, you can still get quite a lot of information across in binary. There are over 1 million combinations of 20-digit binary numbers (2^20 = 1,048,576).

This quiz was reviewed by FunTrivia editor rossian before going online.
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Most Recent Scores
Jan 29 2023 : marianjoy: 7/10
Dec 25 2022 : john62450: 7/10
Dec 24 2022 : jonathanw55: 2/10
Dec 15 2022 : mcdubb: 9/10

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This quiz is part of series All About Numbers:

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1. Five Plus Two is What? Average
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