Question

One pen costs Rs.15 and one pencil costs Rs.3. What is the total cost of x pens and y pencils?

Answer 1

Hint: We are given the cost of one pen and one pencil. Now, when we want to find the cost of some number of pens and pencils, we should note that when we buy x pens the total cost would be given by x times the cost of one pen. Similarly, that when we buy y pencils the total cost would be given by y times the cost of one pencil. Then the total cost would be given by the sum of the cost of pens and pencils.

Complete step-by-step answer:

In this case it is given that the cost of one pen is Rs.15.

When we buy x pens, the total cost would be equal to x times the cost of one pen. Therefore,

$\text{Cost of x pens}=x\times Rs.15=Rs.15x..........(1.1)$

Also, the cost of one pen is given to be Rs.3.

When we buy y pencils, the total cost of pencils would be equal to y times the cost of one pencil. Therefore,

$\text{Cost of y pencils}=y\times Rs.3=Rs.3y.............(1.2)$

Therefore, the total cost would be given by

Total cost= Cost of x pens+ Cost of y pencils = Rs.15x +Rs.3y= Rs.(15x+3y)

Which is the answer to the given question.

Note: In this case the cost of one pen and one pencil were given to be 15 and 3. In the case where the cost of one pen and one pencil are different the factors in equation (1.1) and (1.2) will change accordingly.