**Definition**

How many describes the number of objects or things. And this topic is related to mental arithmetic such that arithmetical calculations performed in the mind, without writing figures down or using a calculator.Watch How Many Videos to learn more.

**How Many **

Mental arithmetic such that arithmetical calculations performed in the mind, without writing figures down or using a calculator. How many means that the number of objects.

For eg: How many fingers in a hand ?

The answer is 5. We just calculate this in our mind neither by writing nor by using calculator.

Another eq: Adds two single digit numbers mentally.

Ordinal number:

Eg: The ordinal number of 1 is first. The ordinal number of 2 is second , etc…

**Addition of 5**

When adding 5 to a digit greater than 5, it is easier to first subtract 5 and then add 10.

For example,

7 + 5 = 12.

Also 7 – 5 = 2; 2 + 10 = 12.

**Subtraction of 5**

When subtracting 5 from a number ending with a a digit smaller than 5, it is easier to first add 5 and then subtract 10.

For example,

23 – 5 = 18.

Also 23 + 5 = 28; 28 – 10 = 18.

**Multiplication by 5**

It’s often more convenient instead of multiplying by 5 to multiply first by 10 and then divide by 2.

For example,

137×5 = 1370/2 = 685.

**Division by 5**

Similarly, it’s often more convenient instead to multiply first by 2 and then divide by 10.

For example,

1375/5 = 2750/10 = 275.

**How Many Videos**

Useful for CBSE, ICSE, NCERT & International Students

Grade : 1

Subject : Maths

Lesson : How Many

Topic: How Many Videos

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