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Weighing things at home
Discover Mathematics P2: Term 1, Lessons 41–50
GoalCompare masses with a balance, read balance pictures, and estimate before weighing.
New words
balance · a tool that compares the mass of two thingsheavier · has more masslighter · has less masslevel · both pans at the same height
Explanation
A balance compares mass. Put one thing in each pan. The heavier thing makes its pan go down, and the lighter thing goes up. If both pans stay at the same height, the two things have the same mass, and we say the balance is level. Before you weigh, make an estimate. Hold both things and guess which is heavier. Then use the balance and see if you were right. You can also put kilogram weights in one pan to find the mass of a thing.
Worked examples
The book is in the left pan and the pencil is in the right pan. The left pan is lower, so the book is heavier.
Two bags of rice, 1 kg each, are in the pans. The balance is level, so they have the same mass.
A melon in the left pan balances 2 kg and 1 kg in the right pan. So the melon is 2 + 1 = 3 kg.
Class activity
A coat-hanger balance. Hang a bag on each end of a coat hanger and hang the hanger from a door handle or a string. Put one small thing in each bag, such as a spoon and a pencil, an apple and an orange. First guess which side will go down, then see.
Practice
1
In the picture, which side is heavier, the left or the right?
The right side, because it is lower.
2
A bag of sugar is 1 kg. How many bags make 4 kg?
4 bags.
3
The balance is level. The left pan holds 3 kg. How much is in the right pan?
3 kg.
4
Estimate: is a pencil closer to 5 g or 5 kg?
5 g.
5
Hana’s bag is 4 kg. Salma’s bag is 3 kg. Whose bag is heavier?
Hana’s bag, because 4 is more than 3.