Quantitative Techniques Flashcards

A sum doubles itself in 10 years at simple interest. What is the annual interest rate?

Answer: 10%

SI = P when it doubles, so P = (P × R × 10)/100, giving R = 10%.

A 20% increase followed by a 20% decrease results in what net change?

Answer: −4%

Net factor = 1.20 × 0.80 = 0.96, representing a 4% decrease.

If 8 workers can complete a job in 15 days, how many days will 12 workers take?

Answer: 10

Total work = 8 × 15 = 120 man-days; 12 workers need 120/12 = 10 days.

A car's value depreciates by 15% each year. What is its value after 2 years if bought for $20,000?

Answer: $14,450

Value = 20000 × (0.85)² = 20000 × 0.7225 = $14,450.

The average of five numbers is 40. If one number is removed, the average becomes 35. What is the removed number?

Answer: 60

Sum of 5 = 200; sum of 4 = 140; removed number = 200 − 140 = 60.

A rectangle's length is increased by 20% and width decreased by 10%. What happens to its area?

Answer: Increases by 8%

New area factor = 1.20 × 0.90 = 1.08, so area increases by 8%.