Previous Year Questions

Price of one blue pen = Rs.15

Price of one red pen = Rs.20

In shop A:

Let the number of blue and red pens sold are A_b and A_r respectively. Then,

Then, A_b + A_r = 32...(i)

And 15A_b + 20A_r = 580

3A_b + 4A_r = 116..(ii)

From (ii) - 3(i), we get

4A_r - 3A_r = 116 - 3 * 32

A_r = 20

A_b = 32 - 20 = 12

So, selling price of blue pens = 12 * 15 = Rs.180

And selling price of red pens = 20 * 20 = Rs.400

In shop C:

Let the number of blue and red pens sold are A_b and A_r respectively. Then,

Then, A_b + A_r = 20...(iii)

And 15A_b + 20A_r = 370

3A_b + 4A_r = 74..(iv)

From (iv) - 3(iii), we get

4A_r - 3A_r = 74 - 3 * 20

A_r = 14

A_b = 20 - 14 = 6

So, selling price of blue pens = 6 * 15 = Rs.90

And selling price of red pens = 14 * 20 = Rs.280

In tabular form:

Let the number of blue pens sold by shop D and E are 2x and x respectively.

Let the number of red pens sold by shop D = number of red pens sold by shop E = y

Then, 28 = 2x + y => y = 28 - 2x

And selling price received by shop E = 15 * x + 20 * y = 310

3x + 4y = 62

Now, 3x + 4 * (28 - 2x) = 62

3x + 112 - 8x = 62

5x = 50

x = 10

Then, number of red pens sold from shop D = 28 - 2x = 28 - 2 * 10 = 8