Subtraction of Units of Mass/Weight

Lesson Plan of Subtraction of Units of Mass/Weight

Subject Mathematics

Grade III

Students` Learning Outcomes

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

Information for Teachers

  • Write the values vertically under column headings (g and kg)
  • Large value in upper row and small value in bottom row.
  • To find the difference of weights, grams are subtracted from grams and kilograms from kilograms.
  • If the grams column has a smaller number on top, the numbers on top borrows from the number to its left then adds into it, then find the difference. 1kg = 1000g

Subtraction of Units of Mass/Weight

  • Repeat the key words for subtraction, how much left, reduced, lighter, heavier, how much etc.
  • While teaching the lesson, also consult textbook where and when applicable.

Material / Resources

Writing board, chalk/marker, duster, pointer/stick, balance, weights and weight textbook

Introduction

  • Ask from students;
      • A bar of chocolate weighs 100g. Abu eats 40g. How much is left?

Subtraction of Units of Mass/Weight

      • In May, Sameer weighed 52kg. In June, his weight had reduced to 48kg. How much weight did he lose?

Subtraction of Units of Mass/Weight

Development

Activity 1

  • Write the statement on board.
  • At a construction site there was 350kg 950g of sand. If there are 49kg 375g of sand is used in a material. How much sand is left?

Subtraction of Units of Mass/Weight

  • Ask the following questions to the students:
      • What was the total weight of sand? (350kg950g)
      • How much sand was used in material? 49kg375g)
      • How we find the remaining weight of sand? (by construction)
  • Write their response on the board.

Subtraction of Units of Mass/Weight

  • Ask them to solve it.
  • Subtract grams from grams, as such; 950g – 378g = 675g.
  • Now subtract “kg” from “kg”, as such; 350kg – 49kg = 301kg, hence, the remaining weight of sand is 301kg675g.
  • Write another statement on the board.

Subtraction of Units of Mass/Weight

  • Ask the following questions to the students.
  • What was Ali`s weight with shoes? (45kg15g)
  • What was the weight of shoes? (1kg150g)
  • Which operation will we use to find the actual weight of Ali?(Subtraction)
  • Write their responses on board under the heading of units(kg and g)

Subtraction of Units of Mass/Weight

  • Ask one student to solve it on the board.
  • Ask them how we subtract 150g from 15g? (we borrow 1kg from 5kg)
  • How many grams are there in 1kg?(1000g)
  • Now how many grams we have? (1018g)

Subtraction of Units of Mass/Weight

  • Hence, actual weight of Ali is 43kg 868g.

Activity 2

  • Ask students to solve the following sums in their notebook.

Subtraction of Units of Mass/Weight

  • Tell them, firstly subtract grams from grams.
  • Tell them, if the grams column has a smaller number on top, the numbers on top borrows from the number to its left then adds into it, then find the difference. 1kg = 1000g
  • Observe their work and guide them where necessary.
  • Revise the relation between “g” and “kg” by asking from the students.

Sum up / Conclusion

  • Conclude that:
      • To find the difference of weights, grams are subtracted from grams and kilograms from kilograms.
      • If the grams column has a smaller number on top, the numbers on top borrows from the number to its left then adds into it, then find the difference. 1kg =1000g

Assessment

  • Ask the following questions to the students;
      • Which is the smaller unit of weight?
      • Which unit is used to weigh heavier objects?
      • Which mathematics operation is performed for finding the difference between the weights of two objects?

Follow up

  • Ask students to find the difference of weight of any two daily grocery items, like; rice 2kg 500g, red chili 250gm etc.
  • Ask the students to solve the questions given in the textbook.

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