Second Term Lesson Note for Week Six
Class : Primary 4
Subject : Mathematics
Topic : Estimation (Rounding Off Numbers)
Duration : 80 minutes
Period : Double Periods
Reference Book :
- New Method Mathematics for Primary Schools, Book 4, by Learn Africa.
- Lagos State Unified Schemes of Work for Primary Schools (Primary 4 – 6)
- Online Resources
Instructional Material : Chart showing numbers round up and numbers to round down.
Learning Objectives : By the end of the lesson , learners will be able to :
i. Explain estimation in relation to rounding off numbers
ii. Round off whole numbers and decimal numbers
iii. Perform estimation operations
Previous Knowledge : Learners are familiar with rounding off numbers
Content :
Estimation involves rounding off numbers. In rounding off numbers, a number can either be rounded up or rounded down.
Rounded up : Numbers from the range of 5 to 9 are rounded up to one (1), and it is added to the number that precedes it (value stated as required).
Rounded down : Numbers from 0 to 4 are rounded down to zero (0), and added to the number that precedes it (value stated as required).
The value stated may be rounding off to tens, hundreds, thousands for whole numbers, while for decimal numbers, it is rounded off to nearest whole number.
For examples:
A. Round off to the nearest tens:
i. 13 = 10 ( This is because 3 is rounded down to zero and it is added to 1 tens, which now gives 1tens)
ii. 69 = 70 (This is because 9 is rounded up to one and it is added to 6 tens, which now gives 7 tens)
iii. 415 = 420 (to nearest tens because, 5 is rounded up to one and it is added to 1 tens which now gives 2 tens, while the 4 is hundreds and remain the same).
B. Round off to nearest hundreds:
i. 075 = 100 (to nearest hundreds, because 7 in 075 is tens and the decider which is rounded up to 1 and added to zero to give 100)
ii. 341 = 300 (to nearest hundreds, because 4 in 341 is tens and the decider which is rounded down to zero and added to 3 to give 300)
iii. 6187 = 6200 ( to nearest hundreds, because 8 in6187 is tens and the decider which is rounded up to one is added to 1 to give 6200)
C. Round off to the nearest whole number.
i. 3.2 = 3 ( The 2 is tenth and it is rounded down to zero and added to 3 to give 3)
ii. 946.5 = 947 ( The whole number is 946, then 5 is the decider which is rounded up to 1 and it is added to 946 to make 947)
iii. 18.8 = 19 ( The whole number is 18, then 8 is the decider which is rounded up to 1 and it is added to 18 to give 19)
iv. 7.49 = 7 ( The 7 is whole number, 4 is the decider which is rounded down to zero and added to 7 to give 7.
Presentation Step:
Step 1 : Revision of the previous lesson taught with the learners by asking questions orally.
Step 2 : Explain the concept of rounding off numbers.
Step 3 : Solve examples involving whole numbers and decimal numbers
Step 4 : State the steps in estimating numbers
Evaluation: The teacher examined the lesson by given them some exercise to do.
1. Round off to the nearest tens:
i. 75 = ____________
ii. 34 = ___________
2. Round off to the nearest hundreds:
i. 341 = ___________
ii. 187 = __________
iii. 4693 = ____________
3. Round off to the nearest thousands:
i. 7500 = ______________
ii. 6178 = _____________
iii. 2999 = ____________
4. Round off the following to the nearest whole number:
i. 5.8 = ___________
ii. 100.25 = ____________
Conclusion : At the end of the lesson, learners were able to answer the questions correctly. The teacher moves round and makes necessary corrections.