Concept of Product Constancy

Concept of Product Constancy

It is the same as we know the inverse proportion in the chapter of ratio, proportion and variation.

eg., when the rate of pencil is rs.1.25 then we can purchase 16 pencils by paying rs.20. If the rate of a pencil is decreased  by rs.0.25 then we can purchase 20 pencils by paying rs.20.

Explanation: 

Rate x No. of Pencils = Price

1.25 x 16 = 20
1.00 x 20 = 20

so you can see that here product 20 is constant in both the cases. Thus it is clear that if we reduce the price of a pencil to rs.0.50, then we can purchase 40 pencils in rs.20.

some more examples of product constancy:

speed x time = distance
rate x time = cost
efficiency x time = work
length x breath = area
average x no of elements = total value
rate x quantity = price

eg., The price of sugar is increased by 25% then by how much per cent should a customer reduce the consumption (ie., quantity used) of sugar so that he has not to increase his expenses on sugar.

price x quantity = expenditure

100 x 100 = 10,000
125 x X = 10,000

x = 10,000/125 = 80. Therefore, % reduction = 20%

or

1 x1 = 1
 1.25 x k =1 = > k = 0.8

thus there will be 20% decrease in the consumption of sugar in order to maintain to same expenditure on sugar.