# 4.13 To do mental calculations

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## Memorandum

1.1 9 × 12 = 108

1.2 7 × 8 = 56

1.3 6 × 8 = 48

1.4 13 × 5 = 65

1.5 (4 × 6) + 18 = 42

1.6 (4 × 8 ) + 8 = 40

1.7 144 ÷ 12 ÷ 6 = 2

1.8 2 004 – 13 = 1991

1.9 54 ÷ 6 = 9

1.10 63 ÷ 7 = 9

1.11 132 ÷ 12 = 11

1.12 4 × 4 × 4 = 64

1.13 72 ÷ 9 = 8

1.14 ( 81 ÷ 9) × 4 = 36

1.15 15 × 7 × 6 × 0 = 0

## Activity: to do mental calculations [lo 1.9]

1. It has been a long time since we checked to see how good your mental arithmetic skills are! See if you can complete the following mental arithmetic test within two minutes:

1.1 9 × 12 =

1.2 7 × 8 =

1.3 6 × = 48

1.4 × 5 = 65

1.5 (4 × 6) + 18 =

1.6 (4 × ) + 8 = 40

1.7 ÷ 12 ÷ 6 = 2

1.8 2 004 – 13 =

1.9 54 ÷ = 9

1.10 ÷ 7 = 9

1.11 132 ÷ 12 =

1.12 4 × 4 × 4 =

1.13 72 ÷ = 8

1.14 ( ÷ 9) × 4 = 36

1.15 15 × 7 × 6 × = 0

Fill in: I got ____________________________________________ correct!

## 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 performs mental calculations.

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