Answer: Option D

Explanation:
A = (x/100)y = xy/100   .................(Equation 1)
B = (y/100)x = yx/100.................(Equation 2)
From these equations, it is clear that A = B

Answer: Option B

Explanation:
Let total number of men = 100
Then
80 men are less than or equal to 50 years old
(Since 80% of the men are less than or equal to 50 years old)
=> 20 men are above 50 years old (Since we assumed total number of men as 100)20% of the men above the age of 50 play football⇒Number of men above the age of 50 who play football = 20 × 20/100 = 4
Number of men who play football = 20 (Since 20% of all men play football)
Percentage of men who play football above the age of 50 = 420 × 100 = 20%
=>Percentage of men who play football less than or equal to the age 50 = 100% − 20% = 80%

Answer: Option C

Explanation:
Let x is the maximum marks of the examination
Marks that Arun got = 30 % of x = 30x/100
Given that Arun failed by 10 marks
⇒Minimum Pass Mark = 30x/100 + 10......(Equation 1)
Marks that Sujith got = 40 % of x = 40x/100
Given that Sujith got 15 marks more than the passing marks
⇒40x100=Minimum Pass Mark +15
⇒Minimum Pass Mark =40 x100 −15......(Equation 2)
From equations 1 and 2, we have
30 x 100 + 10 = 40x/100 − 15
⇒10x/100 = 10 + 15 = 25
⇒x/10 = 25
⇒ x = 10 × 25 = 250
⇒Maximum marks of the examination = x = 250
Substituting the value of x in Equation 1, we have
Minimum Pass Mark = 30x/100 + 10 = 30 × 250/100 + 10 = 75 + 10 = 85

Answer: Option A

Explanation:
Given that height on 15th birthday = 159 cm and growth = 6%
Let the previous year height = x
Then height on 15th birthday = x × (100 + 6)/100 = x × 106/100
⇒159 = x × 106/100 
⇒x = 159 × 100/106 = 1.5 × 100 = 150 cm

Answer: Option A

Explanation:
Assume that the initial price of 1 Litre petrol = Rs.100 ,Benson spends Rs.100 for petrol,
such that Benson buys 1 litre of petrol
After the increase by 25%, price of 1 Litre petrol = 100 × (100+25)/100 = Rs.125
Since Benson spends additional 15% on petrol,
amount spent by Benson = 100× (100+15)/100 = Rs.115
Hence Quantity of petrol that he can purchase = 115/125 Litre
Quantity of petrol reduced = (1−115/125) Litre
Percentage Quantity of reduction = (1−115125)/1 × 100 = 10/125 × 100 = 105 × 4 = 2 × 4 = 8%