Subject: Mathematics-Geometry
Duration: 40 minutes
Grade: 5 Primary /Elementary
General Aim: Development of Skills /Acquisition of Information
Specific Aims: To lead children through observation and experimentation, to an understanding of area and to define the method for calculating area of a rectangle.
Basic Method: Reasoning
Preparation: Teacher: Has prepared sufficient papers of various shapes and sizes. One foot squares and board diagrams are in readiness.
Note: This lesson was given using inches and feet. One inch squares of paper are easier for children to manipulate than one centimetre squares. The exercise could be done with reference to "square units" and then applied to relevant units of measures in use.
Reference:
Step
1: Perimeter is the distance around
the extremity / periphery / border. e.g Hemming a piece of cloth,
trimming lawn edges (PERIMETER) vs Ironing the cloth, mowing
the lawn (AREA) i.e area is surface covered Perimeter is measured by
feet/inches etc. How can area be measured? Presentation of Relevant
Data The meaning of perimeter is
recalled through questioning. Using board illustrations the
teacher leads children to distinction between perimeter and
area. The term "area" is introduced if not given by
children. Teacher poses the problem of
measuring the perimeter and area of a rectangular
object. Step
2a: Paper shapes, books, pencil cases
etc. Observation of
Data Free: Children freely
explore coverage of surface using papers of various shapes
and sizes including one inch squares. Step
3: Anticipated findings: e.g. Area is
most easily expressed using same sized units. The smallest
at our disposal is a one inch square. Formulation of Rule
(Generalisation) Children comment on findings.
Similarities are emphasized through repetition and further
teacher questioning. Step
2b: Printed examples Directed
Observation Children cover several board
figures of equal area with one inch squares. The number of
pieces is counted in each case. Larger figures indicate the
necessity for using larger square units (square
feet). Children use one inch squares to
measure area of figures on a printed sheet. Step
3b: Figures a, b and c require 6 square
units.i.e. same area is shared by figures differing in width
and length. 3 x 2 = 2 x 3 = 6 x 1 3 sets of 2, or 2 sets of 3, or 6
sets of 1 L sets of W, or W sets of L, or A =
L x W Formulation of the rule Children comment on findings which are noted on the
board. Children attempt written formulation of the rule.Teacher
inspects each child's attempt. Through questioning, teacher seeks possible short method
for calculating the number of squares used in covering
rectangular figures. = 4 x 3 sq ins = 12 sq ins Step 4 Application of the
Rule Children find area of rectangle by
mathematical and diagrammatical means. Findings are
discussed and compared for equivalence. Children are commended for
contributions to the discussion. Children commence recording of
findings.
A = L x W
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