Multiplication

100 × 2 700 = .........................

• Write a rule for multiplying any number by 100:

Does your rule “work” for 0,2 × 100?

Activity 7:

To recognise and use the characteristics of multiplication with whole numbers [lo 1.12.3]

1. In our previous module we looked at the associative and commutative characteristics of addition – do you remember this? There are similar characteristics of multiplication. Do you want to know how it works? Fill in the missing factors to balance the equasions:

8 x 6 = 6 x ____

23 x ____ = 13 x 23

124 x 85 = ____ x 124

2. Is the following true or false?

2.1 6 × 3 × 4 = 3 × 4 × 6 = 4 × 6 × 3 ..................................................

2.2 (2 × 4) × 5 = (5 × 4) × 2 = 4 × (2 × 5) ..................................................

3. What do you realise from the above examples?

Activity 8:

To estimate and calculate by means of rounding off [lo 1.8.1]

1. To be able to estimate answers is an important skill. If you are good at estimating, it will be easier for you to realise that you may have made a mistake in your calculations. Round off the following numbers first and in this way you will be able to estimate what the product of each of the following will be:

BRAIN-TEASERS!

a) Which two numbers, smaller than 10, have 3 factors each?

......................... and .........................

b) Colour in the correct block:

c) Which two numbers have a product of 48 and a sum of 16?

......................... and .........................

Activity 9 :

• To be able to solve problems in context [LO 1.6.1]
• To be able to use a series of techniques to do calculations [LO 1.10]

Let’s do some brainstorming now. Your teacher will give you the necessary paper.

1. Split up into groups of three and, as quickly as possible, make a list of all the means of transportation that exist in our country.

2. Which of the above-mentioned would you choose if you had to travel? Why?

3. Where is your favourite seat in:

1. a car
2. a school bus
3. a boat
4. an aeroplane

4. Now see whether you are able to solve the following problems:

Messrs Slobo, Mugathle and Sisula have each bought a brand new taxi with which to transport passengers. For their first trip their plans are the following:

• Who made the most money with the first trip?
• If the petrol cost R1,05 for every kilometre that was travelled, how much did Mr Mugathle’s petrol account come to?
• If all the passengers in Mr Slobo’s taxi were athletes and they had to run back, how far did they run altogether?
• Explain to the rest of the class how your group calculated the answers.
• Compare your methods. How do your methods differ?
• Check the answers, using a pocket calculator.