Question

If the rate of notebooks is Rs 240 per dozen, what is the cost of 3 notebooks? Also find the cost of 9 notebooks, 24 notebooks and 50 notebooks and complete the following table.

Number of notebooks (x)	12	3	9	24	50	1
Cost (in Rupees) (y)	240	...	...	...	...	20

Answer 1

As the number of notebooks increases their cost also increases. 

∴ Number of notebooks and cost of notebooks are in direct proportion.

i.

∴ y = 3 × 20 

∴ y = 60

ii.

∴ y = 9 × 20 

∴ y = 180

iii. 

∴ y = 24 × 20 

∴ y = 480

iv.

∴ y = 50 × 20 

∴ y = 1000

Number of notebooks (x)	12	3	9	24	50	1
Cost (in Rupees) (y)	240	60	180	480	1000	20