ROUNDING UP AND DOWN
Course / Level: 2º
Eso (compulsory secondary education)
Subject:
Maths
Introduction
Sometimes exact answers to a problem are unnecessary or even impossible, and a sensible approximate answers is needed. In this unit, you will meet a variety of ways of approximating numbers. Then you will use approximate values to find estimates to calculations, to solve problems and see how approximation and measurement are related.
Learning Outcomes:
- To find estimates in practical problems.
- To use rounding in real-life problems.
- To measure accuracy of measurements.
Subject Content:
-
Rounding up and rounding down decimal numbers to the nearest tenth, hundredth and thousandth.
-
Rounding up and rounding down whole numbers to the nearest ten, hundred and thousand.
-
Significant figures.
-
Estimates.
- Accuracy of measurements.
Methodology:
Use of ICT resources (videos,
powerpoint) to introduce concepts and support explanations. Working
in pairs on the worksheets given. Learning by doing and solving
problems. Developing of key competences trying to work out solutions to every-day problems.
Resources:
Videos:
https://www.youtube.com/watch?v=fd-E18EqSVk
(Maths antics)
https://www.youtube.com/watch?v=eCJ76hz7jPM
(Khan Academy)
https://www.youtube.com/watch?v=-UMk8y0Rfig
(UK Maths teacher)
Worksheets:
Powerpoint:
Sessions:
Session 1: introduction
to approximation: the need of an approximate answer for practical
problems. Brainstorming at the beginning of the lesson about the need
of approximation (all students). Video showing of rounding: Maths
antics. Worksheet about rounding whole numbers to the nearest ten,
hundred and thousand: mathsworksheets4kids.
Session 2: briefing
about rounding: showing powerpoint. Rounding whole numbers in
real-life problems: activity 1 and 2 in pairs. Rounding in practical
problems worksheet (examples a, b and c) (in pairs).
Session 3: rounding
decimal numbers to the first/second/third decimal place:
mathsworksheets4kids, link 1 (individual). Video showing about
significant figures: khan academy. Worksheet for finding estimates
for some calculations involving all operations: addition,
subtraction, multiplication and division (groups of 3), link 2.
Session 4:
all measurements are approximate. Brainstorming about accuracy of
measurements. Video showing: uk maths teacher. Worksheet with
practical problems about this topic (in groups of 4), link 3.
One more session may be added
is needed to make sure all students reach the evaluation criteria
about rounding.
TASKS EXAMPLES:
Word problems examples:
1.- The attendance at a
Manchester United soccer match was 61267. Round this number to the
nearest hundred.
2.- In a census, the
population of Wolverhampton was given as 242187. Round this number
a) to the nearest thousand.
b) to the nearest hundred
thousand.
Rounding in practical
problems examples:
a) How many boxes, each
holding 6 eggs, can be filled with 250 eggs? How many eggs are left
over?
b) How many cars, each 4.5 m
long, would fit end to end on a ferry deck which is 31 m long.
c) 190 tiles are needed for a
bathroom. The tiles are sold in boxes of 20. How many boxes are
needed?
Accuracy of measurements
example:
The world record for the
women’s 100 metres is 40.49 seconds.
a) To what degree of accuracy
is this time given?
b) Write down the minimum and
maximum time this could be.
c) What is the maximum
possible error?
