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By now you know how to multiply by smaller numbers. Now we are going to see whether you are also able to do calculations with bigger numbers. Split up into groups of 3 and ask your teacher to give you the paper you need. Then read the instructions very carefully.
Michaela and her friends visited the zoo and heard the following interesting facts: a hippopotamus eats 45 kg of fodder per day, while a large bull elephant needs 225 kg of fodder per day!
1. How many kilograms of fodder will 329 hippopotamuses eat per day?
2. How many kilograms of fodder must the zoo buy per day to feed 76 bull elephants?
3. If the entrance fee was R15 per person and 475 people visited the zoo that day, how much money was taken at the entrance gate?
4. Explain to the rest of the class how your group calculated the answers.
5. Compare your methods. How do the various methods differ from each other?
6. Use a pocket calculator to check the answers.
1. In the previous activity you probably noticed that there is more than one method to do multiplication. Split up into groups of 3 again. Look carefully at the solutions to the following problem and explain the methods to one another.
Mrs Cele sells clothes. There are 46 different pairs of jeans and 238 different shirts. How many combinations can she make up?
1.1 I calculate 46 × 238 in this way
238 × 46 = (200 + 30 + 8) × (40 + 6)
200 × 40 = 8 000
30 × 40 = 1 200
8 × 40 = 320
200 × 6 = 1 200
30 × 6 = 180
8 × 6 = 48
10 948
1.2 I write it in this way:
238
× 46
48 (8 × 6)
180 (30 × 6)
1 200 (200 × 6)
320 (40 × 8)
1 200 (40 × 30)
8 000 (40 × 200)
10 948
1.3 My method looks like this:
^{2} 2 ^{4} 3 8
× 4 6
1 4 2 8
9 5 2 0
1 0 9 4 8
2. Now use any method that you understand and with which you feel comfortable, and calculate the product of:
2.1 576 × 47
2.1 576 × 47
CHALLENGE!
Can you calculate the product of the following by using the method shown in 1.3?
1. 347 × 251
2. 526 × 438
ANOTHER BRAIN-TEASER
Study the following sum carefully: 24 × 13 = 377
One of the digits is incorrect. Can you find out which one it is? ..............
What must it be? .........................
Let’s go out to dinner.
This assignment is for your portfolio. Your teacher will go through it with you and explain exactly what you are expected to do. Make sure that you understand perfectly before you start. Remember to work neatly.
Read the following menu carefully:
Form groups of three. Your group decides to eat something from each section of the menu. To make it easier for the waiter, each person in your group chooses the same soup, starter, main course and dessert.
Decide what you are going to order and then calculate your account. Use the block below. You may use a calculator. First estimate what the meal will cost the group. ..............................
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