Question

Drawing pencils cost 80 paise each and colour pencils cost 1.10 rupees each.If altogether two dozen pencils cost 21.60 rupees.how many colour pencils are there

Answer 1

Let the number of drawing pencils be x

Let the number of colour pencils be y

Altogether there are 2 dozens i.e, 2(12) = 24 number of pencils.

Total number of pencils = 24

x + y = 24

x = 24 - y -----eq(I)

Cost of each drawing pencil = 80Paise = 80/100 = Rs. 0.8 (Since Rs. 1 = 100 Paise)

Cost of drawing pencils = 0.8x = 0.8(24 - y) = 19.2 - 0.8y(From (I))

Let the number of colour pencils be y

Cost of each colour pencil = Rs. 1.1

Cost of colour pencils = 1.1 × y = Rs. 1.1y

Total cost of colour pencils and drawing pencils = Rs. 21.6

19.2 - 0.8y + 1.1y = 21.6

0.3y + 19.2 = 21.6

0.3y = 21.6 - 19.2

0.3y = 2.4

y = 2.4/0.3

y = 24/3

y = 8

Therefore the number of colour pencils are 8.

Answer 2

Let x be the number of drawing pencils and y be the number of coloured pencils.

There are two dozen pencils in total.

Thus, we have

Suppose the number of drawing pencil = x

number of coloured pencil = 24-x

The rate of a drawing pencil is 80 paise and the rate of a coloured pencil is Rs.1.10.

The total price of drawing pencils and coloured pencils is Rs.21.60.

Thus, we have

0.80x + 1.10(24-x) = 21.60

0.8x + 26.4 - 1.1x = 21.6

-0.3x = -4.8

x = 16

so, number of drawing pencils = 16

number of coloured pencils = 24-16 = 8