Percentage change = (Original amount - New amount)/Original amount

Correct Option: C

Here, Z = 100, X = 80 and Y = 72
Now according to the formula,
Percentage change = (Original amount - New amount)/Original amount
= [(80 - 72)/80] x 100%
= (8/80) x 100%
= 10%
∴ Y is less by X = 10%

Let x% candidates take both the subjects.
Percentage of candidates who opted Physics = 65.8%
and percentage of candidates who opted Mathematics = 59.2%
∴ x = (65.8 + 59.2 - 100)% = (125 - 100)% = 25%

Correct Option: B

Let x% candidates take both the subjects.
Percentage of candidates who opted Physics = 65.8%
and percentage of candidates who opted Mathematics = 59.2%
∴ x = (65.8 + 59.2 - 100)% = (125 - 100)% = 25%
Also, total number of candidates = 2000
∴ Number of candidates who opted both the subjects
= 25 x 2000/100 = 500

Percentage of car owners = 80%
Percentage of mobile phone owners = 60%
Percentage of people having both car and mobile phone = 55%
Percentage of people having only car = 80 - 55 = 25%
Percentage of people having only mobile phone = 60 - 55 = 5%

Correct Option: C

Percentage of car owners = 80%
Percentage of mobile phone owners = 60%
Percentage of people having both car and mobile phone = 55%
Percentage of people having only car = 80 - 55 = 25%
Percentage of people having only mobile phone = 60 - 55 = 5%
Percentage of people having a car or a mobile phone or both = 55% + 25% + 5% = 85%

Percentage population = 150000 x (1 + 2/100) x {1 + (5/2)/100} x (1 + 4/100)

Correct Option: A

Percentage population = 150000 x (1 + 2/100) x {1 + (5/2)/100} x (1 + 4/100)
= 150000 x (102/100) x (41/40) x (104/100)
= 163098

Number of failures = 10% of 950 + 40% of 250

Correct Option: A

Number of failures = 10% of 950 + 40% of 250
= (10/100) x 950 + (40/100) x 250 = (95 + 100) = 195
Fail percentage = [195/(950 + 250)] x 100
= (195/1200) x 100 = 16.25%