TOPIC: ARITHEMATIC

SUB – TOPIC: ROUNDING OFF NUMBERS

RATIONALE

• Rounding off helps us to get numbers with less digits which are easier to use.
• We also round off numbers because we want all our numbers to have the same degree of accuracy.
• We also round off numbers because the instrument to measure the number can measure to a certain degree of accuracy.

PRE – REQUISITE SKILLS AND KNOWLEDGE

• Place value of a digit in a given number
• Number of decimals in a given number
• Measurement of length and angles

TEACHING / LEARNING RESOURCES

• A mathematical set
• Tape measure or blackboard ruler

ACTIVITIES

• Discuss with the learners the importance of numbers in our daily lives. Let them state different types of numbers they know.
• Mark two points on the ground 10 m apart. Let one point be the zero mark and the other point the 10 m mark.  Let students stand at the 0, 1, 2, ……., 10 marks.

Ask students to determine those nearer the 0 mark and those nearer the 10 m mark.

• Mark the 10.1 m mark on the ground and 10.2 m mark on the ground.  Place small objects at 10.1, 10.11, 10.12, 10.13, ………., 10.2 m. Ask students to determine those closer to 10.1 and those closer to 10.2.

CONCLUSION

When rounding off, identify the digit that will be the final digit in the rounded number. If the first digit on the right of this digit is 0, 1, 2, 3, 4 the digit remains the same, if the first number is 5, 6, 7, 8, 9, increase the digit by 1.

EXAMPLES

• Round off the following numbers to the nearest tenth: (i) 9.16, (ii) 123.68, (iii) 98.72, (iv) 0.43
• Round off to the nearest tens: (i) 24, (ii) 658,
• Round off to the nearest hundredth: (i) 0.278, (ii) 6.7449, (iii) 8.9976