Subtraction
Category : 4th Class
LEARNING OBJECTIVES
This lesson will help you to:—
Real Life Example
Subtraction is used in every sphere of our life. It is used in our daily activities like purchasing grocery, all monetary transactions like banks etc.
More on top?????
No need to stop.
More on the floor?????
Go next door, get ten more.
Numbers the same?????
Zero’s the game.
QUICK CONCEPT REVIEW
WHAT IS SUBTRACTION?
Subtraction is taking away some objects from a given collection. It is taking one number away from another.
Some other names used in subtraction are Minus, Less, Difference, Decrease, Take Away, Deduct.
TERMINOLOGY
Difference
The result obtained after subtraction is called difference.
It the result obtained after subtracting one number from another.
Minuend
The number that is to be subtracted from is called minuend.
Subtrahend
The number that is to be subtracted is called subtrahend.
MINUEND – SUBTRAHEND = DIFFERENCE
For example, 50 - 20 = 30
Here, Minuend = 50
Subtrahend = 20
Difference = 30
PROPERTY OF SUBTRACTION
For example: 6884 – 6884 = 0
For example: Monty saw 9 mangoes on a mango tree.
He wants to eat the mangoes but could not reach them. How many mangoes were left on the tree?
There were 9 mangoes on the tree. Monty could not get any mango. It means still there were 9 mangoes on the tree.
This can be written as 9 – 0 = 9
Therefore, there were 9 mangoes left on the tree.
Hence, we can say that when we subtract zero from a number, the answer is the number itself.
SUBTRACTION WITH NUMBER LINE
72 – 45 =?
5 + 20 + 2 = 27
Therefore, 72 - 45 = 27
USES OF SUBTRACTION
Here we have to find the number of students who were left unselected. Whenever we have to find how many are left we use subtraction.
Amazing Fact
The above question can solved with an amazing shortcut also.
5000 – 1832 =?
5000\[\to \]5000-1\[\to \]4999
-1832\[\to \]1832-1\[\to \]1831
________________________________
3168
Therefore, number of students left unselected = Total number of students - Number of students selected = 75 - 25 = 50
To compare groups: A Bakery had 52 pastries & 95 cookies. How many more cookies are there than pastries?
There are 2 groups:
(a) Pastries and
(b) Cookies
Now to compare the quantity of 2 groups, we will subtract the smaller group from the larger group.
This is shown as follows;
95 cookies
-52 pastries
___
43 more cookies than pastries.
1. To find what does not belong to a group: Ben has 15 dogs. Out of them 5 are pugs. Find out how many dogs are not pugs.
Total number of dogs = 15
Number of Pugs = 5
To find the number of dogs which do not belong to the group of pugs, we will subtract the number of pugs from total number of dogs.
Therefore, 15 - 5 s 10 dogs are not pugs.
To find what was taken away: A farmer loaded a truck with 1129 apples. On the way, some apples fell on the road. On unloading, the farmer found that there are only 1000 apples. Find out how many apples fell from the truck.
Here we know the original number & the number which is left over. We need to find the number of apples taken away.
This can be written as follows:
1129 - ? = 1000
Therefore, the number of apples which fell from the truck are = 1129 – 1000 = 129
To find how many more are needed: A thirsty crow needs 1255 pebbles to put in the pot to raise the water level. But he has only 255 pebbles. How many more pebbles does he need?
225 + ? = 1255
The number of pebbles required = 1255 – 255 = 1000 more pebbles.
SUBTRACTING FOUR DIGIT NUMBER
1. Without Regrouping/Borrowing: There are 2549 seats in a circus tent. 2138 people came to see the circus show. How many seats were left vacant?
To find out the number of vacant seats we will use subtraction as follows:
No. of vacant seats = Total no. of seats – no. of seats occupied by people.
= 2549 – 2138
Th H T O
2 5 4 9
+ 2 1 3 8
_______________
0 4 1 1
Therefore, 411 seats were left vacant.
2. By Regrouping/Borrowing: Out of 2138 people who came to see the circus, 1619 were adults. Find out how many children were there? (See the previous circus figure.)
Total number of children = Total number of people – Total number of adults
= 2138 – 1619
This can also be written as:
Th H T O
1 11 2 18
- 1 6 1 9
_______________
0 5 1 9
SUBTRACTING WITH ZEROS
5000 – 1832=?
OR
Th H T O
5 0 0 0
- 1 8 3 2
_______________
3 1 6 8
There are not enough ones, tens or hundreds and we can't regroup from zero.
Therefore, we will make 0 into 10 & then regroup as shown below.
Reduce 5 by 1. 5 becomes 4 & 0 becomes 10. Now reduce 10 by 1.10 becomes 9 & 0 becomes 10. Repeat this process & subtract. The result is shown below.
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