1.16 Fun with the pocket calculator

Mathematics

Having fun with pocket calculators and negative numbers

Educator section

Memorandum

10. a) 32 x 64 = M+

156 + MR = 2 204

1. 244 ÷ 61 = M+

236 – MR = 232

11. -8 + (-1) + (9) = 0

-3 + 6 + (8) = -5

(6) + (-1) + -4 = 1

13. a) 27

b) 74

c) 39

d) 15

e) 51

f) 132

g) 9

h) 102

i) 41

j) 51

k) 4

l) 1 000

m) 3 800

n) 100

o) 21

14. a) Number smaller than 0

1. Lifts; Temperature, depth under the sea

15. a) Learner gives own answer

1. -1

-3

-5

c) 3; 0; -3; -6; -9; -12; -15; -18; -21; -24

16. a) -6

b) 8

c) 13

d) -14

Leaner section

Content

Activity: fun with the pocket calculator [lo 1.9.2

10 CHALLENGE

If you do not know the sequence in which you have to do calculations, the pocket calculator will not be of any help to you - it will actually help you out of the frying pan into the fire!

Use the memory keys on your pocket calculator to determine the correct answers. Write down what you key in:

a) 156 + 32 × 64

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b) 236 – 244 ÷ 61

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11. BRAIN TEASER

Complete the following. Remember the correct order of operations!

12. SELF-ASSESSMENT

Indicate which is true of you:

13. TIME FOR MENTAL CALCULATION

Complete the following as quickly and accurately as possible:

a) 13 + 5 + 9 = ___________________

b) 12 + 28 + 34 = ___________________

c) 94 – 19 – 36 = ___________________

d) 78 – 35 – 28 = ___________________

e) 29 + ___________________ = 80

f) ___________________ ÷ 12 = 11

g) 63 ÷ ___________________ = 7

h) one eighth of 816 = ___________________

i) (3 × 12) + 5 = ___________________

j) 3 × (12 + 5) = ___________________

k) 18 × ___________________. × 25 = 1 800

l) 56 × 5 × ___________________ = 56 000

m) 25 × 38 × 4 = ___________________

n) 1 400 ÷ ___________________ = 14

o) one quarter of 84 = ___________________

This time I have done ___________________________________

14. CLASS DISCUSSION: NEGATIVE NUMBERS

Discuss the following and find the answers:

a) What is a negative number?

b) Where are negative numbers used in everyday life?

c) Draw or cut and paste examples of these from magazines, newspapers, etc. in the space provided.

+ - 15. REMEMBER

When keying in – 5, press – 5 on you pocket calculator, OR 5

a) How does YOUR pocket calculator show negative numbers? (What must you key in?)

b) Key in the number 7 on your pocket calculator. Subtract 2. Subtract 2 again.

Subtract 2 again. Subtract 2 again. What do you get? .........................

Subtract 2 once more. Write down what your screen shows. .........................

Subtract 2 again. What does the pocket calculator show now? .........................

+ - c) Use the constant function of your pocket calculator to program it to count from 6 in -3s. (6 + 3 = = =) Write down the first 10 answers.

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16. Use your pocket calculator to do the following exercise. Remember the order of the operations. You may also make use of the memory function. Write down everything that you key in to obtain the answer.

a) 13 – (11 + 8)

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b) (-3) + 4 + (-2) + 9

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c) -8 + 3 × (-5 + 12)

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d) -2 + 8 – 6 + (-4) – 9 + 12 + (-13)

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Assessment

Learning Outcome 1: The learner will be able to recognise, describe and represent numbers and their relationships, and to count, estimate, calculate and check with competence and confidence in solving problems.

Assessment Standard 1.9: We know this when the learner uses a range of techniques to perform calculations including:

1.9.2: using a calculator.