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
- 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;
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- A bar of chocolate weighs 100g. Abu eats 40g. How much is left?
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- In May, Sameer weighed 52kg. In June, his weight had reduced to 48kg. How much weight did he lose?
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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?
- Ask the following questions to the students:
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- 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)
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- Write their response on the board.
- 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.
- 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)
- 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)
- Hence, actual weight of Ali is 43kg 868g.
Activity 2
- Ask students to solve the following sums in their notebook.
- 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:
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- 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
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Assessment
- Ask the following questions to the students;
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- 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?
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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.
