# Lesson Planning of Subtraction of Units of Length

Lesson Planning of Subtraction of Units of Length

Subject Mathematics

Students` Learning Out comes

• Subtract measures of length in same units with and without borrowing.
• Solve real life problems involving same units of length for subtraction with and without borrowing.

Information for Teachers

• Same units of measurement can be subtracted.
• Centimeter can be subtracted from centimeter
• Meter can be subtracted from meter.

• Milometer can be subtracted from kilometre.
• While teaching the lesson, the teacher should also consult textbook at all steps wherein and whenever it is required.

Material / Resources

Writing board, chalk/marker, duster, pointer, ruler, meter rod, and measuring tape

Introduction

• If you have ten pieces of chocolate and you gave three pieces to your friends.  How many pieces are left?
• Similarity if a piece of string is cut the length of the string is reduced and we can find the new length of the string.

Development

Teaching Approach

Demonstration, discussion

 Activity 1 (Problem solving) Ask following questions from the students: Length of a lead pencil is 14 cm. after sharpening its length is reduced by 2 cm. find the length of the pencil after sharpening? Ask from students, as; What is the length of pencil before sharpening? How much length is reduced? Which operation can be formed to find the new length of the pencil? Then demonstrate how to solve this problem? Length before  sharpening  the pencil     =  1 4 cm Length after sharpening  the pencil          =    2 cm Length after sharpening the pencil          =  1 2 cm Suppose, the distance between your home and the school is 499 m. you have traveled 218 m, while going from home to school. How much distance is there you still have t travel? Ask from students: as; What is the total distance? How much distance is covered? Which operation can be formed to find the distance to be covered? Then demonstrate how to solve this problem: Total distance                         =   4  9  9 m Distance traveled                   = – 2 1   8 m Distance to be still covered    =  2  8   1 m

 Activity 2 Demonstrate how to solve the following subtraction questions: as;       Centimeter,                 Centimeter          4 9 cm                           8  5 cm       – 3  7 cm                         -2  4 cm          1 2 cm                           6 1 cm          Meter,                         Meter             3  5 m                          8  5 m            -1 2 m                        – 6  2 m             2 3 m                           2  3 m            Kilometre,                Kilometre 1         9    8 km          1   8  5 km              –           7    6 km             – 8  5 km             1   2     2 km            1  0  0 km

Sum up / Conclusion

• How we could find the difference between the lengths?
• Can we different units?
• Which is the smaller unit of length?

Assessment

• Ask the students to find the difference between lengths:
1. 60 cm –      20 cm   = ———?
2. 86 km –      52 km    = ——–?
3. 150 cm –    45 cm = ———-?
4. 100 km –    89 km = ———-?
• Teacher is required to involve the students in solving the problems given in the exercise at the end of unit/chapter.