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NCERT Solutions: Comparing Quantities (Old Questions)

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Question 1. Find selling price (SP) if a profit of 5% is made on

(a) a cycle of Rs 700 with Rs 50 as overhead charge.

(b) a lawn mower bought at Rs 1150 with Rs 50 as transportation charges.

(c) a fan bought for Rs 560 and expenses of Rs 40 made on its repairs.

Solution:

(a) ∵ Total cost price = Rs 700 + Rs 50 (Overhead expenses) = Rs 750

Profit = 5% of Rs 750
= (5/100) × Rs 750
= (5 × 750) / 100 = Rs 3,750 / 100 = Rs 37.50
Now, SP = CP + Profit
= Rs 750 + Rs 37.50
= Rs 787.50

(b) ∵ Total cost price = Rs 1150 + Rs 50 (Overhead expenses)
= Rs 1,200
∴ Profit = 5% of Rs 1,200
= (5/100) × Rs 1,200
= (5 × 1,200) / 100 = Rs 6,000 / 100 = Rs 60
Now, SP = CP + Profit
= Rs 1,200 + Rs 60
= Rs 1,260

(c) ∵ Total cost price = Rs 560 + Rs 40 (Overhead expenses)= Rs 600

∴ Profit = 5% of Rs 600
= (5/100) × Rs 600
= (5 × 600) / 100 = Rs 3,000 / 100 = Rs 30
Now, SP = CP + Profit
= Rs 600 + Rs 30
= Rs 630

Question 2. A shopkeeper bought two TV sets at Rs 10,000 each. He sold one at a profit 10% and the other at a loss of 10%. Find whether he made an overall profit or loss.

Solution: Total CP of both TVs = 2 × Rs 10,000
= Rs 20,000
For 1st TV: CP = Rs 10,000
Profit rate = 10%
∴ Profit = 10% of Rs 10,000
= (10/100) × Rs 10,000 = Rs 1,000

∴ SP of 1st TV = Rs 10,000 + Rs 1,000 = Rs 11,000

For 2nd TV: CP = Rs 10,000
Loss rate = 10%
∴ Loss = 10% of Rs 10,000
= (10/100) × Rs 10,000 = Rs 1,000
∴ SP of 2nd TV = Rs 10,000 - Rs 1,000 = Rs 9,000
Now, Total SP of both the TVs = Rs 11,000 + Rs 9,000
= Rs 20,000
∵ Total cost price = Total selling price
∴ There is no overall profit or loss.

Question 3. Find the buying price of each of the following when 5% ST is added on the purchase of 

(a) A towel at Rs 50

(b) Two bars of soap at Rs 35 each

(c) 5 kg of flour at Rs 15 per kg

Solution:

(a) Cost of the towel = Rs 50
∴ Sales tax on the towel = 5% of Rs 50
= (5/100) × Rs 50 = Rs 250 / 100 = Rs 2.50
Thus, the buying price of the towel = Rs 50 + Rs 2.50
= Rs 52.50

(b) ∵ Cost of the two soap bars = (Rs 35) × 2 = Rs 70
∴ Sales tax = 5% of Rs 70
= (5/100) × Rs 70 = Rs 350 / 100 = Rs 3.50
Thus, the buying price = Rs 70 + Rs 3.50
= Rs 73.50

(c) ∵ Cost of 5 kg of flour = Rs 15 × 5 = Rs 75
∴ Sales tax = 5% of Rs 75
= (5/100) × Rs 75 = Rs 375 / 100 = Rs 3.75
Thus, the buying price = Rs 75 + Rs 3.75
= Rs 78.75

Question 4. If 8% VAT is included in the prices, find the original price of

(a) A TV bought for Rs 13,500  (b) A shampoo bottle bought for Rs 180 

Solution:

(a) Cost of TV including VAT = Rs 13,500
Rate of VAT = 8%
Let the original price = Rs x
∴ x + 8% of x = Rs 13,500
or x (1 + 8/100) = Rs 13,500
or x × 108/100 = Rs 13,500

∴ x = Rs 13,500 × 100 / 108 = Rs 13,500 ÷ 1.08 = Rs 12,500
Thus, the original price = Rs 12,500. 

(b) Let original price = Rs x

∴ Price including VAT = x + 8% of x = x × 108/100

But the price including VAT = Rs 180

∴ x × 108/100 = Rs 180
or x = Rs 180 × 100 / 108

or x = Rs 180 × 25 / 27 = Rs 4,500 / 27 = Rs 166.66

Thus, the original price = Rs 166.66

The document NCERT Solutions: Comparing Quantities (Old Questions) is a part of the Class 8 Course Mathematics (Maths) Class 8.
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FAQs on NCERT Solutions: Comparing Quantities (Old Questions)

1. What are the key concepts involved in comparing quantities?
Ans. The key concepts involved in comparing quantities include understanding ratios, percentages, and their applications in real-life situations. Ratios express the relationship between two quantities, while percentages represent a quantity as a fraction of 100. These concepts help in making comparisons and informed decisions based on quantitative data.
2. How can percentages be calculated from fractions?
Ans. Percentages can be calculated from fractions by multiplying the fraction by 100. For example, to convert the fraction ¾ into a percentage, you would calculate (¾) × 100 = 75%. This means that ¾ is equivalent to 75% when expressed as a percentage.
3. What is the importance of understanding profit and loss in comparing quantities?
Ans. Understanding profit and loss is crucial in comparing quantities as it allows individuals and businesses to evaluate financial performance. Profit indicates the gain from a sale after deducting costs, while loss signifies a decrease in value. By comparing these quantities, one can make informed decisions regarding pricing, sales strategies, and overall financial health.
4. How do you find the percentage increase or decrease between two quantities?
Ans. To find the percentage increase or decrease between two quantities, you can use the formula: [(New Quantity - Old Quantity) / Old Quantity] × 100. If the result is positive, it indicates an increase; if negative, it indicates a decrease. This calculation helps in assessing changes in values over time.
5. What role does the concept of simple interest play in comparing quantities?
Ans. The concept of simple interest plays a significant role in comparing quantities, especially in finance. It is calculated using the formula: Simple Interest = Principal × Rate × Time / 100. Understanding simple interest allows individuals to compare investment choices or loans, as it helps in determining the total amount payable or receivable over a specified period.
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