The number data type

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Quick Questions

Shade in the A or B circle for each question.

1. Which one is a number in JavaScript?

A let age = "13";

B let age = 13;

2. Which value is a decimal number?

A 3.5

B "3.5"

3. Which one is a negative number?

A let temp = -2;

B let temp = "-2";

4. What does 5 + 5 give?

A 10

B 55

5. Which statement is true?

A 5 and "5" are both numbers

B 5 is a number and "5" is a string

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1let score = 3.5;		Alet total = 7 + 3;
2let temp = -2;		BStores a negative number. The minus sign is part of the number, and it still has no quotes.
3A whole number with no quotes is a number, so you can calculate with it		CThe quotes make "13" a string, so age + 2 joins the text and prints 132 instead of adding to give 15. Remove the quotes: let age = 13;
4A value in quotes is a string, not a number, even if it looks like a number		DA decimal number uses a full stop, not a comma. Write let price = 3.50; so it is one number.
5let age = "13"; console.log(age + 2);		EStores a decimal number. It has no quotes, so JavaScript treats it as a number you can calculate with.
6let price = 3,50;		Flet answer = "5";

Definitions

number

Fill in the Blanks

Complete each line of code by filling in the missing parts.

let lives = 3; console.log(lives _ 2);

// negative number: minus two let change = __;

// decimal number: three and a half let price = ___;

let a = 5; let b = "5"; console.log(typeof _); // number

let n = 7; console.log(typeof n); // ______

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A let price = 3.5;

B let qty = 4;

C let total = price x qty;

D console.log(total);

Question 2

A let score = 7;

B let bonus = 3;

C let total = score + bonus;

D console.log(type of total);

Question 3

A let a = 1.5;

B let b = 2.5;

C let c = 3,5;

D console.log(a + b + c);

Question 4

A let n = "5";

B let total = n + 2;

C console.log(total);

Question 5

A let big = 1,000;

B let half = big / 2;

C console.log(half);

Answer Key

The number data type

Section A: Quick Questions

B — let age = 13;

A — 3.5

A — let temp = -2;

A — 10

B — 5 is a number and "5" is a string

Section B: Match the Pairs

let score = 3.5; → Stores a decimal number. It has no quotes, so JavaScript treats it as a number you can calculate with.

let temp = -2; → Stores a negative number. The minus sign is part of the number, and it still has no quotes.

A whole number with no quotes is a number, so you can calculate with it → let total = 7 + 3;

A value in quotes is a string, not a number, even if it looks like a number → let answer = "5";

let age = "13"; console.log(age + 2); → The quotes make "13" a string, so age + 2 joins the text and prints 132 instead of adding to give 15. Remove the quotes: let age = 13;

let price = 3,50; → A decimal number uses a full stop, not a comma. Write let price = 3.50; so it is one number.

Section C: Definitions

number — A value written without quotes, whole (7), decimal (3.5) or negative (-2), that you can calculate with. 5 is a number but '5' in quotes is a string, which is text.

Section D: Fill in the Blanks

let lives = 3;
console.log(lives + 2);

// negative number: minus two
let change = -2;

// decimal number: three and a half
let price = 3.5;

let a = 5;
let b = "5";
console.log(typeof a); // number

let n = 7;
console.log(typeof n); // number

Section E: Spot the Error

C — The letter x is not a multiplication operator in JavaScript. Numbers are multiplied with *, so the line should be let total = price * qty;

D — typeof is one word. Writing 'type of' with a space is a syntax error. It should be console.log(typeof total); which prints number.

C — Decimal numbers use a full stop (decimal point), not a comma. A comma here is a syntax error. It should be let c = 3.5;

A — Quotes make "5" a string, which is text. Then n + 2 joins the text and prints 52 instead of adding to make 7. It should be let n = 5;

A — Numbers are written without commas. The comma causes a syntax error. It should be let big = 1000;