Question

If the cost of 15 pens is Rs.148.50. Then the cost of one pen is
A.Rs.12.80
B.Rs.8.90
C.Rs.10.90
D.Rs.9.90

Answer 1

Hint: In this question, we need to determine the cost of a pen such that the cost of 15 pens is Rs.148.50. For this, we will follow the concept of unitary method. To find the cost of each pen we will divide the total given cost by the given number of pens.

Complete step-by-step answer:
Given the cost of 15 pens is Rs.148.50.
This means that the total cost of 15 pens is Rs.148.50.
According to the unitary method, we can evaluate the value of the dependent parameter by carrying simple arithmetic operations such that the value of the parameter in the unit of one is first calculated and then, scaled by the desired amount.
Now, we have to find the cost of each pen and we know the cost of 15 pen so to find the cost of each 15 pen we will divide the total cost of by number of pens which is 15, hence we get
Cost of each pen \[ = \dfrac{{148.50}}{{15}} = Rs.9.90\]
Therefore the cost of one pen is\[ = Rs.9.90\]
So, the correct answer is “Option D”.

Note: Unitary method is the method of determining the quantity of the parameter which is dependent on some other parameter. Proportionality is a very important concept in Mathematics. Here, the cost of a pen is dependent on the number of pens and so the unitary method is applicable easily for the parameters.