We will discuss about addition and subtraction of measuring mass. When there are two objects; we guess which is heavier and which is lighter. Guess depends on experience, feeling by eyes and weighing the objects in our hand span or palm.
We can also say which object is heavier and which is lighter with the help of a simple balance. A balance has two pans and a beam. The exact mass is measured with the help of a balance and weights. We know, about the weights of one kilograms, 500 grams, 250 grams, etc.
One kilogram is the measure of mass of an object having one kilogram of weight. Its abbreviation is kg. Grams abbreviation is g.
1 kg = 1000 g
or, 1000 g = 1 kg
Gram is a part of one kilogram, if it is divided in 1000 equal parts.
½ kg = 500 g
or, 500 g = ½ kg
500 grams weight is half of one kilogram.
250 g = ¼ kg
250 grams weight is one-fourth of one kilogram.
Addition and subtraction of measuring mass:
Say we have to buy some wheat from a shop. The shopkeeper weighs 5 kg once and then 3 kg. Find how much wheat we have bought.
First the shopkeeper weighs 5 kg of wheat
Then he weighs 3 kg of wheat
Total amount of wheat = 5 kg + 3 kg = 8 kg
Thus, we have to add or subtract masses of weights of objects.
1. Mary purchased 2 kg apples, 3 kg pears and 5 kg mangoes. Find the total weight of fruits purchased.
Apples = 2 kg
Pears = 3 kg
Mangoes = 5 kg
Therefore, total weight of fruits purchased = 2 kg + 3 kg + 5 kg = 10 kg fruits
2. (i) Subtract 453 grams from 765 grams
(ii) Convert 5 kg 300 g into g.
(i) 765 grams
- 453 grams
(ii) 5 kg 300 g = 5 × 1000 g + 300 g
= 5000 g + 300 g
= 5300 g