# Lesson Notes By Weeks and Term - Senior Secondary 1

Enlargement and reduction of plain figures 2

TERM – 2ND TERM

WEEK SEVEN

Class: Senior Secondary School 1

Age: 15 years

Duration: 40 minutes of 5 periods each

Date:

Subject: Technical Drawing

Topic: ENLARGEMENT AND REDUCTION OF PLAIN FIGURES 2

SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

I.) Enlarge given objects.

II.) Reduce given objects.

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers, demonstration, videos from source

INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures,

INSTRUCTIONAL PROCEDURES

PERIOD 1-2

 PRESENTATION TEACHER’S ACTIVITY STUDENT’S ACTIVITY STEP 1 INTRODUCTION The teacher identify enlargement processes and guide students to enlarge given objects. Students listens attentively to the teacher STEP 2 EXPLANATION Teacher discusses the procedures for reduction and also guide students to reduce given objects. Students exhibit attentiveness and active engagement STEP 3 NOTE TAKING The teacher writes a summarized note on the board The students copy the note in their books

NOTE

ENLARGEMENT AND REDUCTION OF PLAIN FIGURES 2

Basically, the instrument used for enlargement and reduction is the scale rule. But it possible to do enlargement and reduction of small figures on paper by construction.

For example: An object is given to be enlarge with a ratio of 1:2

Procedure

1. Draw an oblique line from a suitable corner. For instance point A

2. Sum up the total of the numbers in the given ratio 1:2

i.e 1 + 2 = 3

Mark from point A mark 3 equal divisions on the oblique line

3. Draw a straight line from point 1 to point B at the end of line AB

4. Project line AB more to the right. Now, draw a line parallel to line 1B from point 3 to intersect with the projected line at C.

5. From point A, project lines to pass through each corner of the object.

6. From point C, draw main lines parallel to each side of the object.

An object is given to be reduce an object to a ratio of 5 : 3

Procedure

1. Draw an oblique line from a suitable corner. For instance point A

2. The highest number in the given ratio 5 : 3 is 5. From point A mark 5 equal divisions on the oblique line.

3. Draw a straight line from point 5 to point B at the end of the line AB

4. Draw a line parallel to line 5B, from point 3 to intersect with line AB at C

5. From point A project lines to pass through every corner of the object.

6. From point C, draw main lines parallel to each side of the object

EVALUATION: 1. Hexagonal based pyramid is cut by a plane Q.Q. as shown below. Draw, using scale 2:l. (WAEC)

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively