Question

* Cost of a pencil is Rs 2 and eraser
is Rs. 1. Find the cost of 20 sets
of pencil and eraser.​

Answer 1

Assume the cost of a Pencil is x, cost of Eraser is y and cost of Sharpener is z.

Then, cost of 2 pencils, 5 erasers and 7 sharpeners is Rs. 30. Thus,

2x + 5y + 7z = 30 …. (1)

Further, given cost of 3 pencils and 5 sharpeners is Rs. 15 (Assuming Rs. 1.50 is typo) more than 6 erasers. So,

3x + 5z = 6y + 15

3x - 6y + 5z = 15 …. (2)

Now, we need to find the difference of cost between 39 erasers + 1 sharpener and cost of 6 pencils. Thus, we need to compute 39y + z - 6x.

If we multiply Equation (1) by 3 and Equation (2) by -4 and then add these, we get:

-6x + 39y + z = 30.

So, the answer is Rs. 30.

Important Note: Generally, to solve equations in 3 unknowns, we require 3 equations. However, here the third equation can be derived from first 2 equations, so two equations are sufficient to find the answer. But, these equations are insufficient to find the cost of pencil, eraser or sharpener.

Answer 2

Answer:

Cost of one pencil - rs 2

cost of one eraser - rs 1

cost of 20 sets

of pencil and eraser - (2×20) + (1×20)

= 40 + 20

= 60 rupees

Step-by-step explanation:

Hope it helps u ｡◕‿◕｡