Percentage - Study Mode

[#311] In an examination, 30% and 35% students respectively failed in History and Geography while 27% students failed in both subjects. If the number of students passing the examination is 248, find the total number of students who appeared in the examination.
Correct Answer

(B) 400

Explanation

Solution: Percentage of failed candidates = (30 + 35 - 27)% = 38% Percentage of passed candidates = (100 - 38)% = 62% Let the total number of students appeared be x Then, 62% of x = 248 ⇒ x = $$frac{248 × 100}{62}$$ ⇒ x = 400

[#312] In an examination, the percentage of students qualified to the number of students appeared from school A is 70%. In school B, the number of students appeared is 20% more than the students appeared from school A and the number of students qualified from school B is 50% more than the students qualified from school A. What is the percentage of students qualified to the number of students appeared from school B ?
Correct Answer

(D) 87.5%

Explanation

Solution: Let number of students appeared from school A = 100 Then, number of students qualified from school A = 70 Number of students appeared from school B = 120 Number of students qualified from school B : = $$frac{150}{100}$$ × 70 = 105 ∴ Required percentage : $$eqalign{
& = left( {frac{{105}}{{120}} imes 100}
ight)\% cr
& = 87.5\% cr} $$

[#313] In an examination, 65% of the students passed in Mathematics, 48% passed in Physics and 30% passed in both. How much percent of students failed in both the subjects ?
Correct Answer

(A) 17%

Explanation

Solution: Pass students in Mathematics = 65% Pass students in Physics = 48% Student pass in both subject Mathematics and Physics = 30% Student only pass in Mathematics = 65 - 30 = 35% Student only pass in Physics = 48 - 30 = 18% Percentage of Failed students in both subjects : = 100 - [ student pass only in Mathematics + student pass only in Physics + student pass in both subject] = [100 - (35 + 18 + 30)] = 17%

[#314] At an election there were two candidate got 38% of votes and lost by 7200 votes. The total numbers of valid votes were :
Correct Answer

(D) 30000

Explanation

Solution: Let the total number of votes = 100x losser candidate get 38% of vote i.e. = 38x and winner will get = 100x - 38x = 62x According to the question, 62x - 38x = 7200 ⇒ 24x = 7200 ⇒ x = 300 Total votes = 100x = 100 × 300 = 30000

[#315] In 2 kg mixture of copper and aluminium, 30% is copper. How much aluminium powder should be added to the mixture so that the quantity of copper becomes 20% ?
Correct Answer

(C) 1000 gms

Explanation

Solution: According to the question, Mixture of copper and aluminium = 2000 gms 30% copper = $$frac{30}{100}$$ × 2000 = 600 gms Aluminium in mixture = 2000 - 600 = 1400gm Now 'x' weight of mixture have and 600 gm copper become 20% of its total weight. i.e. x = $$frac{{600}}{{20}} imes 100 $$ xa0 = 3000gm Total amount of Aluminium in mixture = 3000 - 600 = 2400 Additional aluminium powder added = 2400 - 1400 = 1000gm