Arithmetic and Number Systems Flashcards

The average of five consecutive odd numbers is 11. What is the largest of these numbers?

Answer: 15

If average of 5 consecutive odd numbers is 11, then 11 is the middle (3rd) number. The numbers are 7, 9, 11, 13, 15. Largest = 15.

A sum of money doubles itself in 8 years at simple interest. What is the rate of interest per annum?

Answer: 12.5%

If P doubles to 2P, SI = P. Using SI = PRT/100: P = P×R×8/100 → R = 100/8 = 12.5% per annum.

What is the value of (a + b)² when a = 4 and b = 3?

Answer: 49

(a + b)² = (4 + 3)² = 7² = 49.

If the speed of a vehicle increases by 20%, by what percentage does the time taken to cover the same distance decrease?

Answer: 16.67%

If speed increases by 20%, new speed = 1.2× original. New time = original/1.2. Decrease = (1 - 1/1.2) × 100 = (0.2/1.2) × 100 = 16.67%.

The HCF of 72 and 120 is:

Answer: 24

72 = 2³ × 3² and 120 = 2³ × 3 × 5. HCF = 2³ × 3 = 24.

A man walks at 4 km/h. After walking for 3 hours, he increases his speed to 6 km/h and walks for 2 more hours. What is the total distance covered?

Answer: 24 km

Distance in first 3 hours = 4×3 = 12 km. Distance in next 2 hours = 6×2 = 12 km. Total = 12+12 = 24 km.