Long and Short Class 4 Notes CBSE Maths Chapter 2 [Free PDF Download]

Long and Short : 

• The long and short are the adjectives or parameters to measure something. 

• The two most important terms used while calculating or measuring something are “long and short”. 

• These are the scales of measurement to measure distance , time , height  etc.

• Long is the word used when something measures very big. Long refers to a large value whenever something is measured. 

• Short can be said as opposite to long. It refers to something that measures less or not so big.

Length of Pencils Comparison

The above figure shows the length of two pencils. 

• Yellow pencil is 11 units long.

• Green pencil is 9 units long.

As we know that 9 is smaller than 11. If we compare the lengths of these two pencils, then we can say that, yellow pencil is long and green pencil is short.

Length and Distance:

• Distance is nothing but measurement of a length of some object, say, how long the road is, gives its distance. Distance is how far apart objects are, such as two cities or two points.

Units of Length and Distance : There are several units of distance and most commonly used ones are Millimetres , centimetres, metres ,Kilometres etc.

• Millimetres: Millimetres is a unit of length in the metric system. A millimetre is one thousandth of a metre. It is represented by ‘mm’.

Representation of cm and mm on a Scale

• Centimetres: Centimetres a unit of length in the metric system, equal to one hundredth of a metre. It is denoted by ‘cm’

Representation of cm on a Scale

• Metres: Metres basic or fundamental unit of length in the metric system. It is denoted by ‘m’.
  

• Kilometres: Kilometres is a unit of length in the metric system, it is equal to one thousand metres. It is denoted by Km.  

Solved Example 1: Look for things in your surroundings that are

(i) About 10 centimetres long

(ii) Between 10 and 20 centimetres long

(iii) Less than 1 cm long.

Ans: 

 i. The things that are about 10 cm long are:

 Tea Mug , Cell phones , Hair comb etc

ii. The things that are about 10 cm and 20 cm  long are:

Soft Drinks bottles , Dinner forks , Carrots etc.

iii. The things that are less than 1 cm long are:

Watermelon seed , a single piece of rice , a piece of daal etc.

Solved Example 2: Convert the following into Metres

i. 700 cm 

ii. 3000 mm 

iii. 2 km 

Ans: To convert the following into metres we need to scale between the following and metres.

i. 700 cm 

We know that  100 cm = 1 m , therefore  700 cm can be obtained by multiplying 7 to both sides. i.e 

$Rightarrow 7 (100 cm) = 7 (1 m) $

$Rightarrow 700 cm = 7 m.$

ii. 3000 mm

We know that 1000 mm = 1 m , therefore 3000 mm can be obtained by multiplying 3 to both sides. i.e 

$Rightarrow 3 (1000 mm) = 3 (1 m) $

$Rightarrow 3000 mm = 3 m.$

iii. 2 km

We know that 1000 m = 1 km , therefore 2000 m can be obtained by multiplying 2 to both sides. i.e

$Rightarrow 2 (1000 m) = 2 (1 km) $

$Rightarrow 2 km = 2000 m.$

How Many ?( The Art of Finding Total)

• How many simply means “what number of”. 

• It is usually used to find a multiple of one thing with respect to another.

• For example, how many times Chennai Super Kings have won the IPL? Here winning IPL is the event and we are supposed to find the multiple of it.

• If we say Chennai have won the IPL 4 times , the event winning IPL is multiplied by 4. 

Solved Examples 1: What is the length of rope , if the rope is 6 arms of Roopa and Roopa’s arm is  25 cm long?

Ans: Given , Length of Roopa’s arm = 25 cm. 

The rope is 6 arms , which means 6 times the length of the arm. 

Therefore , the length of rope = $ 6\times 25 = 150 cm$.

Length of the rope is 150 cm.

Long and Short used for Comparison: 

• In order to compare the length of two quantities , we need to find the length of each of them ( that is how long or short they are).

• For example, to say which is longer, thumb or middle finger? First we need to measure them and we can conclude which one is longer.

• So this goes without saying that the length of the middle finger is longer than the thumb.

• Interesting fact: For most people, their arm span is about equal to their height. Mathematicians say the arm span to height ratio is one to one: your arm span goes once into your height.

Arm Span of a Human Being

Solved Examples 1: Who has a longer hand , a new born baby or an adult ?

Ans: It is quite evident and clear that an adult definitely has longer hands compared to a new born baby.

Practice Questions: 

1. The distance between two cities is measured in ?

2. Name any four objects that are 1 m long ?

Answers:

1. Kilometres

2. Guitars, yard sticks , Baseball bats , Doorknob Height etc.,

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