The boys and girls in a collage are in ratio 3 : 2. If 20% of the boys and 25% of the girls are adults, the percentage of students who are not adults is?

? Milk = 90% 0f 40 = 36 litres and water = 4 litres.
Let L litre water to be added in order to make 20% water in new mixture.
? {(4 + L) / (40 + L)} x 100 = 20
? 20 x (40 + L) = 100 x (4 + L)
? 80 x L = 400
? L = 5 litres .

Let the original fraction be p/q
Now, (120% of p) / (90% of q) = 16 / 21
? 4p / 3q = 16/21
? p / q = (16/21) x (3/4) = 4 / 7

Let original price = Rs. 100
Reduced price = Rs. 75
Increase on Rs. 75 = Rs. 25
Increase on Rs. 100 = (25 x 100)/75 % = 33¹/₃ %

Let income = Rs. 100
Then expenditure = Rs. 75 and saving = Rs. 25
New expenditure = 110% of Rs. 75 = Rs. 165 / 2
New saving = Rs. (120 - 165/2) = Rs. 75/2
Increase in saving = Rs. (75/2 - 25) = Rs. 25/2
? Increase% = (25/2) x (1/25) x 100% = 50%

B's salary is less than A's by (30 x 100)/130 % = 23¹/₁₃%

Let the total number of students be 100
Then, n(A ? B) = n(A) + n(B) - n(A ? B) = (72 + 44 - 100)% = 16%
Now,16% of N = 40
? (16 x N) / 100 = 40
? N = (100 x 40) / 16 = 250

Let side of square = 100 cm
Area = (100 x 100)cm² = 10000 cm²
New area = (130 x 130)cm² = 16900 cm²
Increase in area = (6900 / 10000) x 100% = 69%

Let radius of circle = 100 m
New radius = 101 m
original area = [? x (100)² ]m²
New area = [? x (101)² ]m²
Increase% = [? x {(101)² - (100)²} / { ? x (100)²} ] x 100 %
= 201 / 100% = 2.01%

Let length of square = 100 m and breadth of square = 100 m
Area = (100 x 100) m² = 10000 m²
New length = 130 m and breadth = 120 m

New area of rectangle = (130 x 120) m² = 15600 m²
Increase % = (5600 / 10000) x 100 % = 56%

Let length of a rectangle = 100 m,
Breadth = 100 m
New length = 160 m,
New breadth = B meters
Then, 160 x B = 100 x 100
? B = (100 x 100) / 160 = 125/2
Decrease in breadth = (100 - 125/2)% = 37¹/₂%