Percentages: Product Constancy Ratio Exercise

Answers: (b)

Percent decrease = {a/(100+a)} x 100%

Here, a = 25%

So, {25 /(100 + 25)} x 100 = (25/125) x 100 = 20%

Answers: (c)

Percentage increase in price = {a/(100-a)} x 100%

Here, a = 25%

So required increase = {25 /(100 – 25)} x 100 = 100/3%

Answers: (d)

Required increase percent = {a/(100-a)} x 100%

Here, a = 40%

So the required percentage increase is:

{40/(100-40)} x 100

= (40/60) x 100

200/3%

Answers: (b)

Let the CP of each article = Rs. 100

Consumption = 100 units

Initial expenditure = Rs. (100 × 100) = Rs. 10000

New price of article = Rs. 80

Consumption = 120 units

Expenditure = Rs. (120 × 80)= Rs. 9600

Decrease = Rs. (10000 – 9600) = Rs. 400

∴ Percentage decrease = {(400 x 100)/ 10000} = -4%

Alternate Method:

Here, the price is decreased by 20% and the consumption is increased by 20%.

So, the net change in expenditure

= {x – y – (xy /100)}

= {20 – 20 – (400/100 )} = -4%

Hence, the expenditure decreased by 4%.

Answers:(b)

Percentage decrease in the consumption of petrol

Here, a = 20%

Hence, the required percentage decrease

= [{20 /(100 + 20 )} x 100]% = 50/3%