Question

If you can buy 4 pens in Rs. 12. Find the money (in rupees) required to buy 36 pens.
A) 108
B) 120
C) 96
D) 84

Answer 1

Hint: We will first see that the cost of 4 pens is given. Using this information, we will find the cost of one pen. Now, multiply the cost of one pen by 36 to get the cost of 36 pens.

Complete step-by-step answer:
We are given that we can buy 4 pens for 12 rupees.
Rewriting it as:-
Cost of 4 pens = Rs. 12
So, Cost of 1 pen = $Rs.\dfrac{{12}}{4}$ is equal to Rs. 3.
Hence, we have the cost of one pen as Rs. 3.
Rewriting it as:-
Cost of 1 pen = Rs. 3
So, the cost of 36 pens = $Rs.(3 \times 36)$ that is equal to Rs. 108.
Hence, we require 108 rupees to buy 36 pens.

Hence, the correct option is (A).

Note: The students might use an alternate way to find the cost of 36 pens straight from the cost of 4 pens which will require a lot fewer steps.
Alternate Way:- Cost of 4 pens = Rs. 12
Multiplying this equation by 9 on both side:-
Cost of $(4 \times 9)$ pens = $Rs.12 \times 9$ = Rs. 108.
Hence, we got the same answer in just 3 lines.
The word “multiply” is from the Latin multus, meaning “multi” + plex, meaning “fold”—which, in turn, is from the Proto-Indo-European plek, which means “to plait.” Multiplication is another way to repeatedly add a number. In other words, repeated addition like $7 \times 3$ means 7 + 7 + 7 that is adding 7 three times. The inverse of multiplication is division.
Division is splitting into equal parts or groups. It is the result of "fair sharing".
If the dividend is ‘zero’ then any number as a divisor will give the quotient as ‘zero’.