Class 8 Maths Chapter 7 Question Answers - Comparing Quantities

Q1: A number is increased by 20% and then it is decreased by 20%. Find the net increase or decrease per cent.
Ans: Let the number be 100
20% increase
Increased value = 100 + 20 = 120
Now it is decreased by 20%
Decreased value

Net decrease = 100 – 96 = 4
Decrease per cent
Hence, the net decrease per cent = 4%

Q2: A man whose income is ₹ 57,600 a year spends ₹ 43,200 a year. What percentage of his income does he save?
Ans:
Annual income of a man = ₹ 57,600
Amount spent by him in the year = ₹ 43,200
Net amount saved by him = ₹ 57,600 – ₹ 43,200 = ₹ 14,400
Percentage of his annual saving

Hence, the saving percentage = 25%

Q3: Two candidates Raman and Rajan contested an election. Raman gets 46% of the valid votes and is defeated by 1600 votes. Find the total number of valid votes cast in the election.
Ans:
Let the total number of valid votes be 100
Number of votes got by Raman = 46% of 100
Number of votes got by Rajan = 100 – 46 = 54
Difference between the votes = 54 – 46 = 8
8% of Valid votes = 1,600

Hence, the total number of valid votes = 20,000

Q4: A car is marked at ₹ 3,00,000. The dealer allows successive discounts of 6%, 4% and  on it. What is the net selling price of it?
Ans: 
Marked price of the car = ₹ 3,00,000
Net selling price after the successive discounts

Hence, the net selling price = ₹ 2,63,952

Q5: Find the amount of ₹ 6,250 at 8% pa compounded annually for 2 years. Also, find the compound interest.
Ans:



Q6: Vishakha offers a discount of 20% on all the items at her shop and still makes a profit of 12%. What is the cost price of an article marked at ₹ 280?
Ans:
Marked Price = ₹ 280
Discount = 20% of ₹ 280

So selling price = ₹ (280 – 56) = ₹ 224
Let the cost price be ₹ 100
Profit = 12% of ₹ 100 = ₹ 12
So selling price = ₹ (100 + 12) = ₹ 112
If the selling price is ₹ 112, cost price = ₹ 100
If the selling price is ₹ 224, cost price = ₹   = ₹ 200

Q7: A CD player was purchased for ₹ 3,200 and ₹ 560 were spent on its repairs. It was then sold at a gain of %. How much did the seller receive?
Ans: 
Cost price of the CD player = ₹ 3,200
Amount spent on its repairing = ₹ 560
Net cost price = ₹ 3,200 + ₹ 560 = ₹ 3,760

Hence, the required amount = ₹ 4,230

Q8: Ramesh bought a shirt for ₹ 336, including 12% ST and a tie for ₹ 110 including 10% ST. Find the list price (without sales tax) of the shirt and the tie together.
Ans: List price of the shirt
List price of the tie
List price of both together = ₹ 300 + ₹ 100 = ₹ 400

Q9: Find the compound interest on ₹ 31,250 at 12% pa for  years.
Ans:

Hence, compound interest = ₹10, 302

Q10: Find the compound interest on ₹ 48,000 for one year at 8% per annum when compounded half yearly.
Ans:
Principal (P) = ₹ 48,000
Rate (R) = 8% p.a.
Time (n) = 1 year
Interest is compounded half yearly

Therefore Compound Interest = A – P = ₹ (519,16.80 – 48,000) = ₹ 3,916.80.