Weight for Class 4

Have you ever wondered why some things feel heavy like a backpack full of books while others feel light like paper?

In this chapter, the concept of weight is introduced.

What is Weight?

Weight is a measurement that quantifies the heaviness of an object.

When you pick up a book or a delicious apple, you can feel its weight in your hand.

Heavy and Light

If something has more weight, we call it heavy. Think about big rocks, elephants, hippopotami, whales, etc. are heavy.

But if something is not heavy, we call it light. Think about feathers, papers, balloons, cotton, etc. are light.

Measuring Weights

The weight is measured using a weighing balance and weighing scales, shown as:

Units of Weight

The weight can be measured in grams, kilograms, quintals, pounds, ounces, etc.

Metric Units of Weight

In the metric system, we use special units to measure weight. These units help us understand how heavy or light things are:

Here are some of the units we use:

1. Milligram (mg)
2. Centigram (cg)
3. Decigram (dg)
4. Gram (g)
5. Decagram (dag)
6. Hectogram (hg)
7. Kilogram (kg)

Conversions of Units of Weight

When you want to change from a smaller unit to a bigger unit, you multiply the number associated with the smaller unit of weight by 10.

When you want to change from a bigger unit to a smaller unit, you divide the number associated with the bigger unit of weight by 10.

The conversion of one unit to another is shown as:

Here are some common units of weight and how to convert between them:

Kilograms (kg) to Grams (g):

→ 1 kg = 1000 g
→ To convert from kilograms to grams, you need to multiply by 1000.
→ For example, if you want to convert 5 kilograms to grams, then multiply 5 by 1000 like this:
5 kg × 1000 = 5000 g

Grams (g) to Kilograms (kg):

→ 1 g = 1/1000 kg
→ If you want to convert grams to kilograms, you need to divide by 1000.
→ For example, to convert 5000 grams to kilograms divide by 1000:
5000 g ÷ 1000 = 5 kg

Kilograms (kg) to Hectograms (hg):

→ 1 kg = 10 hg
→ To convert from kilograms to hectograms, you need to multiply by 10.
→ For example, to convert 3 kilograms to hectograms, multiply by 10 like this:
3 kg × 10 = 30 hg

Hectograms (hg) to Kilograms (kg):

→ 1 hg = 1/10 kg
→ To convert from hectograms to kilograms, you need to divide by 10.
→ For example, to convert 30 hectograms to kilograms, divide by 10 like this:
30 hg ÷ 10 = 3 kg

Grams (g) to Milligrams (mg):

→ 1 g = 1000 mg
→ If you want to convert grams to milligrams, you need to multiply by 1000.
→ For example, to convert 7 grams to milligrams, multiply 7 by 1000 like this:
7 g × 1000 = 7000 mg

Milligrams (mg) to Grams (g):

→ 1 mg = 1/1000 g
→ To convert milligrams to grams, you need to divide by 1000.
→ For example, to convert 80000 milligrams to grams, divide by 1000 like this:
80000 mg ÷ 1000 = 80 g

Pounds (lbs) to Ounces (oz):

→ 1 pound (lb) = 16 ounces (oz)
→ To convert pounds to ounces, you need to multiply by 16.
→ For example, to convert 5 pounds to grams, multiply by 16 like this:
5 lbs × 16 = 80 oz

Let us solve some more examples to understand them better.

Example 1: Abraham buys 13.68 kilograms of apples and 15.42 kilograms of pears. What is the weight of the basket in grams if the total weight is 31 kg?

a) 2900 g
b) 2100 g
c) 1900 g
d) 900 g

Answer: c) 1900 g

Explanation: 

Total weight of fruits = Weight of apples + Weight of pears
                              = 13.68 + 15.42
                              = 29.1 kg

Total weight (Basket, apples and pears) = 31 kg

Weight of basket = 31 − 29.1
                            = 1.9 kg

Weight of basket in grams = 1.9 ×  1000
                                          = 1900 g

Example 2: The weight of tomatoes is 2/7th of the weight of potatoes. What is the total weight of tomatoes and potatoes in ounces if the weight of potatoes is 84 pounds?

a) 1318 oz
b) 1328 oz
c) 1718 oz
d) 1728 oz

Answer: d) 1728 oz

Explanation: Weight of potatoes = 84 pounds
Weight of tomatoes = ²⁄₇ × 84
                             = 24 pounds

Total weight of tomatoes and potatoes in pounds = Weight of tomatoes + Weight of potatoes
                                                                       = 24 + 84
                                                                       = 108 pounds

Total weight of tomatoes and potatoes in ounces (oz) = 108 × 16
                                                                                     = 1728 oz