Percentage

31. In an examination, 65% of the total candidates passed. If the number of failed candidates is 420, the total number of candidates is:

A. 1000

B. 1200

C. 1500

D. 2000

सही उत्तर: [B]

हल (Solution):
Correct Answer: B) 1200
Solution:

Failed candidates % = 100% - 65% = 35%.

35% of Total = 420 => Total = (420 * 100) / 35 = 1200.

32. If the length of a rectangle is increased by 20% and its breadth is decreased by 20%, its area will:

A. Decrease by 4%

B. Increase by 4%

C. Remain unchanged

D. Decrease by 2%

सही उत्तर: [A]

हल (Solution):
Correct Answer: A) Decrease by 4%
Solution:

Net effect = +20 - 20 + [(20 * -20) / 100] = -4% (4% decrease).

33. A salary of an employee increases by 10% in the first year and 20% in the second year. Find the total cumulative percentage increase in his salary.

A. 30%

B. 32%

C. 35%

D. 28%

सही उत्तर: [B]

हल (Solution):
Correct Answer: B) 32%
Solution:

Cumulative formula: A + B + (AB/100)

= 10 + 20 + (10 * 20 / 100) = 30 + 2 = 32%.

34. 250 quintals is what percent of 2 metric tonnes? (1 metric tonne = 10 quintals)

A. 12.5%

B. 125%

C. 1250%

D. 25%

सही उत्तर: [C]

हल (Solution):
Correct Answer: C) 1250%
Solution:

2 metric tonnes = 2 * 10 = 20 quintals.

Required percentage = (250 / 20) * 100 = 1250%.

35. . If 10% of x is equal to 15% of y, then 20% of x is equal to what percent of y?

A. 20%

B. 25%

C. 30%

D. 40%

सही उत्तर: [C]

हल (Solution):
Correct Answer: C) 30%
Solution:

Given: 10% of x = 15% of y.

Multiply both sides by 2 to get 20% of x:

2 * (10% of x) = 2 * (15% of y) => 20% of x = 30% of y.

36. Income of Rahul is 10% more than Aman's income. Let Aman's income be x% less than Rahul's income. Find x.

A. 9(1/11)%

B. 10(1/11)%

C. 11(1/9)%

D. 9%

सही उत्तर: [A]

हल (Solution):
Correct Answer: A) 9(1/11)%
Solution:

Required % = [10 / (100 + 10)] * 100 = (10 / 110) * 100 = 100/11 = 9(1/11)%.

37. What percentage of numbers from 1 to 70 have 1 or 9 in their unit's digit?

A. 14%

B. 20%

C. 21%

D. 25%

सही उत्तर: [B]

हल (Solution):
Correct Answer: B) 20%
Solution:

Numbers ending in 1: 1, 11, 21, 31, 41, 51, 61 (7 numbers)

Numbers ending in 9: 9, 19, 29, 39, 49, 59, 69 (7 numbers)

Total favorable numbers = 14. Total numbers = 70.

Percentage = (14 / 70) * 100 = 20%.

38. A student multiplied a number by 3/5 instead of 5/3. What is the percentage error in the calculation?

A. 36%

B. 44%

C. 64%

D. 54%

सही उत्तर: [C]

हल (Solution):
Correct Answer: C) 64%
Solution:

Let the number be the LCM of denominators (3 and 5) = 15.

Correct result = 15 * (5/3) = 25.

Incorrect result = 15 * (3/5) = 9.

Error = 25 - 9 = 16.

Percentage Error = (16 / 25) * 100 = 64%.

39. In a mixture of 60 liters, the ratio of milk and water is 2 : 1. If the quantity of water is to be increased to make the percentage of water 50%, how many liters of water should be added?

A. 20 liters

B. 30 liters

C. 40 liters

D. 15 liters

सही उत्तर: [A]

हल (Solution):
Correct Answer: A) 20 liters
Solution:

Milk = (2/3) * 60 = 40 liters, Water = 20 liters.

To make water 50%, the amount of milk and water must become equal.

Milk is 40 liters, so total water should also become 40 liters.

Water to be added = 40 - 20 = 20 liter

40. If the radius of a circle is increased by 50%, its area is increased by:

A. 50%

B. 100%

C. 125%

D. 150%

सही उत्तर: [C]

हल (Solution):
Correct Answer: C) 125%
Solution:

Area depends on the square of radius (r^2).

Net increase = 50 + 50 + (50 * 50 / 100) = 100 + 25 = 125%.

गणित (Aptitude)