Percentages – Aptitude Questions and Answers
Last Updated :
08 Nov, 2024
Percentage is one of the most important concepts in mathematics. Thus making it necessary while solving quantitative aptitude questions.
In this article, we will discuss solved & unsolved problems on percentages.
Prerequisite:
Aptitude Questions on Percentages
Q1: A defect-finding machine rejects 0.085% of all cricket bats. Find the number of bats manufactured on a particular day if it is given that on that day, the machine rejected only 34 bats.
Solution :
Let the total number of bats on that day be n. => 0.085 % of n = 34 => (0.085 / 100) x n = 34 => n = 34 x (100 / 0.085) => n = 40,000 Therefore, total number of bats manufactured on the day = 40,000
Q2: 25 % of a number is 8 less than one-third of that number. Find the number.
Solution:
Let the number be n. => (n / 3) – 25 % of n = 8 => (n / 3) – (n / 4) = 8 => n / 12 = 8 => n = 96 Thus, 96 is the required number.
Q3: Difference of two numbers ‘x’ and ‘y’ (x > y) is 100. Also, 10 % of ‘x’ is equal to 15 % of ‘y’. Find the numbers.
Solution :
We are given that x – y = 100 and 10 % of x = 15 % of y => x – y = 100 and (10 / 100) x = (15 / 100) y => x – y = 100 and 10 x = 15 y => x – y = 100 and 2 x = 3 y => x – y = 100 and x = 1.5 y => 1.5 y – y = 100 => 0.5 y = 100 => y = 200 => x = 1.5 y = 300 Thus, the required numbers are 300 and 200.
Q4: In a gaming event, 75 % of the registered participants actually turned up. Out of those, 2 % were declared unfit for participation. The winner defeated 9261 participants which are 75 % of the total valid participation. Find the number of registered participants.
Solution:
Let the number of registered participants be n. Number of participants who actually turned up = 75 % of n Number of valid participations = 98 % of (75 % of n) [because 2% were invalid] Number of participants defeated by the winner = 75 % of 98 % of (75 % of n) = 9261 => 0.75 x 0.98 x 0.75 x n = 9261 => 0.55125 x n = 9261 => n = 16800 Therefore, number of registered participants = 16800
Q5: In a test, a geek could answer 70 % C++ questions, 40 % C questions and 60 % Java questions correctly. The test had a total of 75 questions, 10 from C++, 30 from C and 35 from Java. A minimum of 60 % in aggregate was required to be considered for interview. The geek could not clear the test and was not shortlisted for interview. Find by how much marks did the geek miss the interview call, given that each question was of 1 mark and there was no negative marking for incorrect answers.
Solution:
We are given that the geek could answer 70 % C++ questions, 40 % C questions and 60 % Java questions correctly and there were total 75 questions : 10 from C++, 30 from C and 35 from Java. => C++ questions answered correctly = 70 % of 10 = 7 => C questions answered correctly = 40 % of 30 = 12 => Java questions answered correctly = 60 % of 35 = 21 => Total questions answered correctly = 7 + 12 + 21 = 40 => Marks secured = 40 x 1 = 40 Now, marks required = 60 % of 75 = 45 => Shortfall in marks = 45 – 40 = 5 Therefore, the geek missed the interview call by 5 marks.
Q6: A geek gave 40% of his retirement money to his wife. He also gave 20 % of the remaining amount to each of his 3 sons. 50 % of the amount now left was spent on miscellaneous items and the remaining amount of Rs. 1,20,000 was deposited in the bank. How much money did the geek get as retirement money?
Solution:
Let the retirement money be Rs. 100 n => Money given to wife = 40 % of 100 n = 40 n, Balance = 60 n => Money given to 3 sons = 3 x (20 % of 60 n) = 3 x 12 n = 36 n, Balance = 24 n => Money spent on miscellaneous items = 50 % of 24 n = 12 n, Balance = 12 n Now, this remaining 12 n is the money deposited in the bank, i.e., Rs. 1,20,000 => 12 n = 1,20,000 => n = 10,000 Therefore, geek’s retirement money = 100 n = Rs. 10,00,000
Q7: A broker charges a commission of 5% on all orders up to Rs.10,000 and 4% on all orders exceeding Rs. 10,000. He remits Rs. 31,100 to his client after deducting his commission. Find the order amount.
Solution :
Let the order amount be Rs. n => Commission charged = 5 % of Rs. 10,000 + 4 % of (Rs. n – 10,000) = Rs. 500 + 0.04 n – 400 => Commission charged = Rs. 100 + 0.04 n Now, amount remitted = Rs. n – (100 + 0.04 n) = 31,100 => 0.96 n – 100 = 31,100 => 0.96 n = 31200 => n = 32500 Therefore, order amount = Rs. 32,500
Q8: A seller marked up the price of an article by 20 % and then gave a discount of 20 %. Find what percent did he lose in the transaction.
Solution:
We know that an increase by n % and a successive decrease by n % is equal to an equivalent decrease of (n/10)2 %. => Net decrease or loss of the seller = (20/10)2 = 4 %
Q9: The price of a commodity increased by 25 %. By what percent should the consumption be reduced so as to keep the expenditure same?
Solution:
We know that if price of increases by P %, the necessary reduction in consumption to avoid increase in expenditure = [( P / (100 + P) ) x 100] % Therefore, reduction in consumption required = (25 / 125) x 100 = 20 %
Q10: If the numerator of a fraction is decreased by 15% and its denominator is diminished by 10%, the value of the fraction is 2 / 9. Find the original fraction.
Solution:
Let the fraction be N / D, where N is the numerator and D is the denominator. => (N – 15 % of N) / (D – 10 % of D) = 2 / 9 => 0.85 N / 0.9 D = 2 / 9 => 85 N / 90 D = 2 / 9 => N / D = 4 / 17 Therefore, the original fraction is 4 / 17
Q11: The population of a town is 1,60,000 in the current year. If it increases at the rate of 5% per annum, what will be the population 3 years from now?
Solution:
We know that if the population is currently P and it increases by R % every year, then, population after ‘n’ years = P x [1 + (R / 100)]n => Population after 3 years = 1,60,000 x [1 + (5 / 100)]3 => Population after 3 years = 1,60,000 x (1.05)3 => Population after 3 years = 1,60,000 x 1.157625 = 185220
Q12: The value of a car is Rs 1,60,000 in the current year. If it depreciates at the rate of 5% per annum, what will be the value of the car 3 years from now?
Solution:
We know that if the value is currently P and it depreciates by R % every year, then, value after ‘n’ years = P x [1 – (R / 100)]n => Value after 3 years = 1,60,000 x [1 – (5 / 100)]3 => Value after 3 years = 1,60,000 x (0.95)3 => Value after 3 years = 1,60,000 x 0.857375 = Rs. 1,37,180
Q13: How much sugar (in KG) must be added to 50 KG of a 2 % sugar solution so as to make the concentration 10 % ?
Solution:
Sugar in initial solution = 2 % of 50 KG = 1 KG Let the sugar added be n KG. => (1 + n) / (50 + n) = 10 / 100 => n = 40 / 9 Therefore, 40 / 9 KG of sugar should be added.
Q14: In an examination, 80% of the students passed in English, 85% in Mathematics, and 75% in both English and Mathematics. If 40 students failed in both subjects, find the total number of students who appeared in the examination.
Solution:
Let the total number of students be 100 n. => Students passed in English = 80 % of 100 n = 80 n => Students passed in Mathematics = 85 % of 100 n = 85 n => Students passed in both English and Mathematics = 75 % of 100 n = 75 n => Total number of students passed in at least one subject = 80 n + 85 n – 75 n = 90 n => Number of students who failed in both the subjects = 100 n – 90 n = 10 n = 40 (given) => n = 4 Therefore, the total number of students who appeared in the examination = 100 n = 400
Practice Problems (Unsolved) on Percentages
1. What is 15% of 80?
2. If a shirt’s price is reduced from $50 to $40, what is the percentage discount?
3. A student scored 85 out of 100 in a test. What is their percentage score?
4. If the population of a town increases from 10,000 to 12,000 in a year, what is the percentage increase?
5. A car’s value depreciates by 20% each year. If the car’s initial value was $25,000, what will its value be after 2 years?
6. In a class of 50 students, 60% are girls. How many boys are in the class?
7. If 75% of a number is 90, what is the number?
8. A company’s profits increased by 15% to $230,000. What were the original profits?
9. If the price of an item increases by 20% and then decreases by 20%, is the final price higher or lower than the original? By what percentage?
10. In an election, candidate A received 55% of the votes, and candidate B received 12,150 votes. How many total votes were cast?
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