SOLVED PAPER 2021 (CDS) (I) (Elementary Mathematics)

Total Questions: 100

31. A trader gives successive discounts of 20%, 10% and 5% respectively. What is the overall discount?

Correct Answer: (b) 31.6%
Solution:

32. A sum of money was invested at simple interest at a certain rate for 5 year. Had it been invested at a 5% higher rate, it would have fetched ₹500 more. What was the principal amount?

Correct Answer: (a) ₹2000
Solution:

33. The difference between the compound interest (compounded annually) and the simple interest on a certain sum of money at 12% per annum for 2 year is ₹72. What is the principal amount?

Correct Answer: (d) ₹5000
Solution:

34. A train travels 600 km in 5 h and the next 900 km in 10 h. What is the average speed of the train?

Correct Answer: (c) 100 km/h
Solution:

35. Walking at (4/5)ᵗʰ of his usual speed, a man is 12 min late for his office. What is the usual time taken by him to cover that distance?

Correct Answer: (a) 48 min
Solution:Let the usual speed of the man be 5x m/min and usual time be y min.
Distance covered by the man = 5xym
Speed of man = (4/3) × 5𝓍
= 4𝓍 m/min
∴ Distance covered by the man
= 4𝓍(y + 12)m
∴ Distance remains same
⇒ 5𝓍y = 4𝓍(y + 12)
5y = 4y + 48
y = 48min

36. The cost price of 100 mangoes is equal to the spelling price of 80 mangoes. What is the profit percentage?

Correct Answer: (d) 25%
Solution:

37. X sells his goods 25% cheaper than Y and 25% dearer than Z. How much percentage is Z's goods cheaper than Y ?

Correct Answer: (b) 40%
Solution:

38. In a mixture of 80 L of a liquid and water, 25% of the mixture is the liquid. How much water should be added to the mixture so that the liquid becomes 20% of the mixture?

Correct Answer: (b) 20 L
Solution:


39. If 20 persons can clean 20 floors in 20 days, then in how many days can 16 persons clean 16 floors?

Correct Answer: (c) 20 days
Solution:

40. Let the work done by (x - 1) men in (x + 1) days be y. Let the work done by (x + 2) men in (x - 1) days be z. If y : z = 9 : 10 then what is the value of x ?

Correct Answer: (a) 8
Solution: