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# Rounding Up and Down

Keywords:
Student Activity:

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Achievement Objectives:

Achievement Objective: NA3-4: Know how many tenths, tens, hundreds, and thousands are in whole numbers.
AO elaboration and other teaching resources

Purpose:

This is a level 3 number activity from the Figure It Out series. It relates to Stage 6 of the Number Framework.
A PDF of the student activity is included.

Specific Learning Outcomes:

round to the nearest ones or tens numbers

Required Resource Materials:
FIO, Level 3, Number, Book 1, Rounding Up and Down, page 17
A classmate
Activity:

This activity highlights the rules used to round numbers up or down. The most difficult rounding rule occurs when the last digit is a 5. The rule here is to round up.
You may wish to compare the mathematics rules for rounding with the way a local shop rounds prices when people pay for an item with cash. This is a necessary application of rounding brought about by the absence of 1 cent and 2 cent coins. Some shops round \$4.98 up to \$5, and others round \$4.98 down to \$4.95.
“Shopping Around” page 17, Measurement, Figure It Out, Levels 2–3 and its accompanying teachers’ notes deal with rounding.
Question 3 shows that in contextual situations, common sense sometimes dictates the way people round. For example, if 94 people were expected to attend a parents’ evening at a school, it might be  more sensible to put out 100 chairs rather than 90.

#### Investigation

This investigation builds on the rounding practice in the activity on this page. Students will need to look for ways to minimise wastage as well as cost.

#### Answers to Activity

1. a. 30
b. 70
c. 90
d. 110
e. 280
f. 1 000
2. a. 2
b. 3
c. 4
d. 8
e. 18
f. 277
3. Answers will vary. Making clothes is one example. Rounding down when cutting material could make the clothes too small. Another example would be buying timber for a house or renovation project.
Investigation
The cheapest solution is for Hirini to buy two 3 m lengths and six 5 m lengths. This is based on the following:
1.8 + 3.2 = 5 m 1.8 + 1.2 = 3 m
1.8 + 3.2 = 5 m 1.8 + 1.2 = 3 m
0.8 + 0.8 + 1 + 2.4 = 5 m 2.4 + 2.4 < 5 m
0.8 + 0.8 + 1 + 2.4 = 5 m 2.4 + 2.4 < 5 m

AttachmentSize
RoundingUpandDown.pdf197.06 KB