Mathematics
Grade 5
Multiplication and division
Module 33
Division
Activity 1:
To be able to do mental arithmetic [lo 1.10]
- You already know how important it is to be able to do mental arithmetic. You also know how important it is to know your tables. Doing mental arithmetic and knowing your tables will help you do division correctly, too. Let us start right away! Do you also like dried sausage ("droëwors")? Work with a friend. Look closely at the two "sausage machines". The one who is first to give the answers is the fastest sausage maker!
Who won?
2. Work on your own and colour in according to the code: 4 = dark grey ; 5 = pink ; 6 = light grey ; 7 = black ; 9 = red.
3. Complete the tables:
| 34 | ||||||||
| 3.1 | Divided by | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
| Remainders | 1 | ............ | ............ | ............ | ............ | ............ | ............ |
| 61 | ||||||||
| 3.2 | Divided by | 2 | 5 | 6 | 7 | 8 | 9 | 10 |
| Remainders | 1 | ............ | ............ | ............ | ............ | ............ | ............ |
4. Let us see how well you do in the following mental test. Complete it as quickly and accurately as you can:
| 4.1 35 – 5 – 5 – 5 = ............ | 4.11 108 – 12 – 12 – 12 = ............ |
| 4.2 64 – 8 – 8 = ............ | 4.12 72 – 9 – 9 = ............ |
| 4.3 42 ÷ 7 = ............ | 4.13 Halve: 612: ............ |
| 4.4 54 ÷ 6 = ............ | 4.14 Halve: 487: ............ |
| 4.5 ............ ÷ 7 = 8 | 4.15 Halve: 1 036: ............ |
| 4.6 ............ ÷ 12 = 6 | 4.16 ............ ÷ 9 = 4 |
| 4.7 28 ÷ 4 = ............ | 4.17 ............ ÷ 8 = 6 |
| 4.8 280 ÷ 4 = ............ | 4.18 60 ÷ ............ = 5 |
| 4.9 280 ÷ 40 = ............ | 4.19 36 ÷ ............ = 4 |
| 4.10 2 800 ÷ 40 = ............ | 4.20 3 600 ÷ 90 = ............ |
DID YOU KNOW?
Division is the inverse of multiplication.
Thus: 5 × 3 = 1515 ÷ 3 = 5 en15 ÷ 5 = 3
When I want to check a division sum, I multiply. When I check a multiplication sum, I divide
Activity 2:
To recognise, describe and use the reciprocal relation between multiplication and division
[lo 1.12.1]
1. Now use your knowledge of the "inverse" to complete the following:
1.1 If 26 × 17 = 442, then 442 ÷ 17 = ................ and 442 ÷ ................ = 17
- If 24 × 30 = 720, then 720 ÷ ................ = 24 and 720 ÷ 24 = ................
DID YOU ALSO KNOW?
When we divide, we do the following:
REPEATED SUBTRACTION
12 ÷ 3 = 12 – 3 – 3 – 3 – 3 = 4
GROUPING
12 ÷ 3: We must divide 12 into 3 equal groups
DIVISION
12 ÷ 3: We must divide 12 equally between 3
123
Activity 3:
To recognise and represent numbers and to describe and compare them [lo 1.3]
1. Let us do revision. Do you remember what happens when we divide any number by 1? Work with a friend and find the answers to the following:
1.1 5 ÷ 1 = .................................. 1.2 86 ÷ 1 = ............................
1.3 359 ÷ 1 = .............................. 1.4 4 625 ÷ 1 = .......................
1.5 32 174 ÷ 1 = .........................
2. Write down a rule for dividing by 1.
BRAIN-TEASER!
If 5 ÷ 1 = 5 and 86 ÷ 1 = 86, then:
1 ÷ 5 = .........................
1 ÷ 86 = .........................
1 ÷ 359 = .........................
1 ÷ 4 625 = .........................
Thus, if 1 is the dividend, then the answer is always a...........................................