Order of operations with brackets

Name:

Date:

Class:

Quick Questions

Shade in the A or B circle for each question.

1. What does console.log(2 + 3 * 4) print?

A 20

B 14

2. Which line correctly works out the average of a and b?

A let avg = (a + b) / 2;

B let avg = a + b / 2;

3. If a = 6 and b = 10, what does a + b / 2 give?

A 8

B 11

4. What does console.log((2 + 3) * 4) print?

A 20

B 14

5. What does 2 * (3 + (4 - 1)) give?

A 12

B 10

Match the Pairs

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

Left column		Right column
1let avg = (a + b) / 2;		AWorks left to right because - is on the same level, so it does 20 - 6 = 14 and then 14 - 4 = 10.
2let result = 20 - 6 - 4;		BThe * runs before the +, so the answer is 16, not 36. It needs brackets: (10 + 2) * 3.
3Nested brackets: JavaScript works out the innermost brackets first, then works outwards.		Clet total = (2 + (3 * 4)) * 5;
4Without brackets, * and / run before + and -, so only the last number is divided.		DAdds a and b first because of the brackets, then divides the total by 2 to get the average.
5let avg = math + english / 2;		Elet avg = a + b / 2;
6let answer = 10 + 2 * 3; // should be 36		FThere are no brackets, so only english is divided by 2 and then math is added. It should be (math + english) / 2.

Definitions

(a + b) / 2

Fill in the Blanks

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

let a = 6; let b = 10; let average = (a _ b) / 2;

console.log((4 + 6) _ 2); // 5

let result = 2 * ((3 + 5) - _); // 14

let x = 20 / 5 _ 2; // 8

let mark = (90 + 72 + 84) / _; // 82

Spot the Error

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

Question 1

A let maths = 80;

B let english = 90;

C let avg = maths + english / 2;

D console.log(avg);

Question 2

A let a = 6;

B let b = 9, c = 12;

C let avg = a + b + c / 3;

D console.log(avg);

Question 3

A let c = 20;

B let f = c * 9 / (5 + 32);

C console.log(f);

Question 4

A let price = 12;

B let total = price + 3 * 4;

C console.log(total);

Question 5

A let x = (2 + (3 * 4) * 2;

B console.log(x);

C console.log(x - 10);

Answer Key

Order of operations with brackets

Section A: Quick Questions

B — 14

A — let avg = (a + b) / 2;

B — 11

A — 20

A — 12

Section B: Match the Pairs

let avg = (a + b) / 2; → Adds a and b first because of the brackets, then divides the total by 2 to get the average.

let result = 20 - 6 - 4; → Works left to right because - is on the same level, so it does 20 - 6 = 14 and then 14 - 4 = 10.

Nested brackets: JavaScript works out the innermost brackets first, then works outwards. → let total = (2 + (3 * 4)) * 5;

Without brackets, * and / run before + and -, so only the last number is divided. → let avg = a + b / 2;

let avg = math + english / 2; → There are no brackets, so only english is divided by 2 and then math is added. It should be (math + english) / 2.

let answer = 10 + 2 * 3; // should be 36 → The * runs before the +, so the answer is 16, not 36. It needs brackets: (10 + 2) * 3.

Section C: Definitions

(a + b) / 2 — Brackets run first, so a + b is added before dividing by 2. Then * and /, then + and -. Operators on the same level go left to right. Without brackets, only b is divided by 2.

Section D: Fill in the Blanks

let a = 6;
let b = 10;
let average = (a + b) / 2;

console.log((4 + 6) / 2); // 5

let result = 2 * ((3 + 5) - 1); // 14

let x = 20 / 5 * 2; // 8

let mark = (90 + 72 + 84) / 3; // 82

Section E: Spot the Error

C — Without brackets, only english is divided by 2 because / runs before +. It should be (maths + english) / 2 so the marks are added first.

C — Division happens before addition, so only c is divided by 3. Brackets are needed around a + b + c so the sum is divided: (a + b + c) / 3.

B — The brackets make JavaScript add 5 + 32 first, then divide by 37. The formula needs c * 9 / 5 + 32, with no brackets, so the multiply and divide run before the add.

B — Without brackets, 3 * 4 is worked out first, giving 24 instead of 60. Brackets are needed so price + 3 is added before multiplying: (price + 3) * 4.

A — The brackets are not paired. The outer opening bracket is never closed. It should be (2 + (3 * 4)) * 2, so the inner brackets run first, then the outer ones.