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Level Three > Number and Algebra

Rounding Up and Down

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.

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