Second Term Lesson Note for Week Three.
Class : JSS 1
Subject : Mathematics
Topic : Addition and Subtraction on Approximation of numbers.
Duration : 80 Minutes
Period : Double Period
Reference Book :
- Essential Mathematics for Junior Secondary School, Book 1.
- Lagos State Unified schemes of work for Junior Secondary School, (JSS 1 – 3)
- Online Resources
Instructional Material : Chart showing the concept of approximation considering whole numbers and decimal numbers.
Learning Objectives : By the end of the lesson learners will be able to :
i. Approximate whole numbers to significant figures
ii. Approximate decimal numbers to significant figures.
iii. Perform Approximation on addition and subtraction of Numbers involving whole numbers and decimal numbers.
Content :
ADDITION AND SUBTRACTION OF APPROXIMATIONS
Recall that when approximating to significant figures, it simply means non-zero digit, starting from left hand side.
Then, you pad it up by adding zeroes to the position of the numbers rounded off.
For example :
Approximate 23745 to :
i. 2 s. f. ii. 4 s.f. iii. 3 s.f.
Solution :
i. 23745 = 24000 (First pick 23*** from the left then the 7 is the decider, which is rounded up to 1 and added to make it 24***. Hence, we pad it up with zeroes to give us 24000) .
ii. 23745 = 23750 ( First pick 2374* from the left hand side then 5 is the decider, which is rounded up to 1 and added to make it 2375*. Hence, we pad it up with zero to give us 23750)
iii. 23745 = 23700 ( First pick 237** from the left hand side then 4 is the decider which is rounded down to 0 and added to make it 237**. Hence pad it up with 00 to give us 23700).
Example 3.1: Approximate the following to it accuracy of degree
i. 674 + 975 ( to 3 s.f. )
ii. 805 + 912 ( to 4 s.f. )
iii. 3076 – 621 ( to 2 s.f. )
iv. 695.728 – 97.979 ( to 4 s.f. )
Solutions :
i. 674 + 975 = 1649 (1650 to 3 s.f.)
Note that you must add the numbers before converting to the degree of approximation.
ii. 805 + 912 = 1717 (1717 to 4s.f.)
Note : After the addition, we have 1717 to 4 sig. Fig., it remains 1717.
iii. 3076 – 621 = 2455 (2500 to 2 s.f.)
iv. 695.728 – 97.979 = 597.749 (597.7 to 4 s.f.)
Presentation Steps :
Step 1 : Revision of the previous lesson with the student.
Step 2 : Introduces the new topic to the students by applying approximation
Step 3 : Explains that the basic operation of addition and subtraction is done, before approximating the answer to the number of significant figures.
EVALUATION :
Convert the following to their accuracy degree
1.) 42.4739 (to 5 s.f)
2.) 67.3258 (to 3 s.f)
3.) 879.9087 (to 4 s.f)
4.) 304.385 (to 5 s.f)
CONCLUSION : The teacher summarizes the lesson all over again and does corrections to the class work given.
ASSIGNMENT:
ESSENTIAL MATHEMATICS BOOK 1
EXERCISE 8.7 NO 1 (g,h,I,j,k,l and m) PAGE 93
EXERCISE 8.8 NO 7,8 and 9 PAGE 95
EXERCISE 8.5 NO 1(D,E,F), NO 4 (B &C) N0 5 (A TO G) PAGE 89