Question

Cost of a dozen pens is Rs 180 and the cost of 8 ball pens is Rs 56. Find the ratio of the cost of a pen to the cost of a ball pen.

Answer 1

Hint: The unitary method, in essence, is all about finding the “per unit value”. The unitary method is a technique for solving a problem by first finding the value of a single unit.

Complete step-by-step answer:
Now use the unitary method to find the value of a single unit.
Cost of a dozen pens (12 pens) \[ = Rs.180\]
Cost of one pen $ = \dfrac{{180}}{{12}}$
 Cost of one pen, ${C_1} = Rs.15$
Now, Cost of 8 ball pens $ = Rs.56$
Cost of one ball pen $ = \dfrac{{56}}{8}$
Cost of one ball pen, ${C_2} = Rs.7$
Now, take the ratio of cost of a pen to the cost of a ball pen.
$\dfrac{{{C_1}}}{{{C_2}}} = \dfrac{{15}}{7}$
So, the ratio of the cost of a pen to the cost of a ball pen is 15:7
Note:Whenever we face such types of problems we use some important points. First we find the value of a single unit by using a unitary method then after the take ratio we can get the required answer.