Unitary means “of one” . Mathematically it means “1”. To know this in an easy way, I am writing few examples.
Question 2: If the cost of 50 pencils is Rs 500. oo . Find the cost of One pencil .
I am modifying the above Sum a little bit .
Question 3: If the cost of 50 pencils is Rs 500.00 . Find the cost of 12 pencil .
Now the basic rule is :
For question 1. If we know the cost or other parameter of one thing , then to know the cost of many thing we will do multiplication .
Here we know the cost of 1 pen . Therefore the cost of 25 pen will be MORE than the cost of 1 one pen.
Here we realize for more value . Therefore we will multiply.
Also watch the image cost of ONE to cost of MANY means MULTIPLY.
Solution 1:
∵ the cost of 1 pen is Rs. 2
∴ the cost of 25 pens is 2×25 [we realize for more value.]
= Rs. 50
For question 2. And if we know the cost of many things or other Parameter , then to know the cost of one thing we will do division.
Here we know the cost of many pencils and we want to know the cost of 1 pencil.
We realise that the cost of 1 pencil will less than the cost of 50 pencils.
Therefore we realise for less value. Therefore we will divide.
Solution 2:
∵ the cost of 50 pencils is Rs. 500
∴ the cost of 1 pencil is 500/25 [we realize for less value. Therefore divide]
= Rs. 20
3rd sum is the combination of two sums. In this sum we will realise both division and multiplication.
Solution 3:
∵ the cost of 50 pencils is Rs. 500
∴ the cost of 1 pencil is 500/25 [we realize for less value. Therefore divide]
= Rs. 20
∴ the cost of 12 pencils is 20×12 [we realize for more value.Therefore multiply.]
= Rs. 240
Now watch this video.
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