Subtraction of Units of Length

Lesson Planning of Subtraction of Units of Length

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Lesson Planning of Subtraction of Units of Length

Subject Mathematics

Grade 3rd

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.

Subtraction of Units of Length

  • 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

  • Ask from students:
  • 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;
  1. What is the length of pencil before sharpening?
  2. How much length is reduced?
  3. 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;
  1. What is the total distance?
  2. How much distance is covered?
  3. 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.

Follow up

  • During morning walk. Ali walks 600 m, but his friend walks 520m. how much distance does Ali walks more than his friend?
  • What is the difference between 452 km and 126 km ?

 

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