LemonmathSelf-study sheet

Grade 3 · Lesson 1.2

The 3 times table and dividing by 3

Name: Date: Time spent: min

Goals

Know the 3 times table, from $3\times 1$ to $3\times 10$ .
Use the 3 times table to divide by $3$ , for example $24\div 3$ .
Solve a word problem with one multiplication or one division.

Remember

In the 3 times table, going down one row adds $3$ to the product, from $3\times 1=3$ to $3\times 10=30$ .
$3\times 5=15$ means $5$ groups with $3$ in each.
To divide by $3$ , find the matching multiplication: $3\times 8=24$ , so $24\div 3=8$ .
Many equal groups: multiply. Sharing equally or making groups: divide. Remember the unit in the answer.

Exercises

Exercise 1

Work out in your head: a) $3\times 5$ ; b) $3\times 8$ .

Exercise 2

Fill in the missing numbers in the pattern: $3, 6, 9, \square, 15, \square, 21$ .

Exercise 3

Work out: a) $18\div 3$ ; b) $27\div 3$ .

Exercise 4

Write $>$ , $<$ or $=$ in the box: $3\times 7 \;\square\; 20$ .

Exercise 5

A teacher shares $15$ pens equally between $3$ children. How many pens does each child get?

Exercise 6

Each row in the school garden has $3$ plant pots. The garden has $10$ rows like this. How many plant pots are there altogether?

Exercise 7

Remember the last lesson: finding a missing number in an addition. Find the missing number: $\square+12=3\times 7$ .

Exercise 8 Challenge

Mrs Hoa has $27$ apples and puts them into bags with $3$ apples in each bag. She gives away $4$ bags. How many apples does Mrs Hoa have left?

Mini test

15 minutes, without looking back at the lesson. Part I: circle one letter; Part II: write T or F for each statement; Part III: write the answer in the box.

Part I. Multiple choice

Question 1.

3\times 6

equals

9

.B.

18

.C.

15

.D.

21

Question 2.

27\div 3

equals

9

.B.

24

.C.

8

.D.

30

Question 3. Which of these is correct?

3\times 4=7

.B.

3\times 7=24

.C.

3\times 5=18

.D.

3\times 9=27

Question 4.

18

cakes are put into boxes with

3

cakes in each box. How many boxes are there?

15

boxes.B.

6

boxes.C.

21

boxes.D.

54

boxes.

Part II. True or false

Question 1. We know that

3\times 8=24

. Look at these calculations.

a) $24\div 3=8$ .	T / F
b) $3\times 9=24+6$ .	T / F
c) $3\times 7=24-3$ .	T / F
d) $24\div 3=21$ .	T / F

Part III. Short answer

Question 1. Ha puts flowers in vases,

3

in each vase. She fills

9

vases. How many flowers does Ha have altogether?

Question 2. A teacher shares

30

sweets equally between

3

children. How many sweets does each child get?

Score: ........ / 10

Hints (only when stuck)

Exercise 1.

What you need: count on in threes, or take the answer from the row above and add $3$ .

Steps:

Part a: count on in threes five times.
Part b: you know $3\times 7=21$ , so add $3$ .

Exercise 2.

What you need: each number in the pattern is $3$ more than the one before it.

Steps:

The number after $9$ is $9+3$ .
The number after $15$ is $15+3$ .

Exercise 3.

What you need: to divide by $3$ , find the multiplication by $3$ that gives the dividend.

Steps:

Part a: $3\times\square=18$ .
Part b: $3\times\square=27$ .

Exercise 4.

What you need: work out the multiplication first, then compare the two numbers.

Steps:

Work out $3\times 7$ .
Compare the result with $20$ .

Exercise 5.

What you need: sharing equally means dividing.

Steps:

What do we know? $15$ pens shared equally between $3$ children. What is asked? How many pens each child gets.
How do we solve it? Work out $15\div 3$ , then check with multiplication.

Exercise 6.

What you need: many equal groups means multiplication.

Steps:

What do we know? $3$ pots in each row and $10$ rows. What is asked? The number of pots altogether.
How do we solve it? Work out $3\times 10$ and write the unit.

Exercise 7.

What you need: the missing addend is the total minus the addend you know.

Steps:

Work out $3\times 7$ to find the total.
Take away $12$ from the total.

Exercise 8.

What you need: this problem has several steps: a division, a subtraction, then a multiplication.

Steps:

Find how many bags there were at first: $27\div 3$ .
Find how many bags are left after giving away $4$ .
Change the bags left into apples.

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