Percentage - Study Mode
[#556] A line of length 1.5 metres was measured as 1.55 metres by mistakes. What will be the value of error percent ?
Correct Answer
(C) $$3frac{1}{3}$$%
Explanation
Solution: Percentage error : = $$frac{1.55 - 1.50}{1.50}$$ xa0 × 100 = $$frac{0.05}{1.50}$$ × 100 = $$frac{5}{150}$$ × 100 = $$frac{5 × 2}{3}$$ = $$frac{10}{3}$$ = $$3frac{1}{3}$$%
[#557] A reduction of 20% in the price of wheat enables Bhuvnesh to buy 5 kg more wheat for Rs. 320. The original rate (in rupees per kg) of wheat was :
Correct Answer
(A) 16
Explanation
Solution: Let the initial expenditure = 100 units Increase in consumption = $$frac{20}{80}$$ = $$frac{1}{4}$$ 1 unit = 5 kg Original consumption = 5 × 4 = 20 kg New consumption = 5 × 5 = 25 kg Original price = $$frac{320}{20}$$ = 16 per kg
[#558] If the height of a cylinder is increased by 15% and the radius of its base is decreased by 10% then the percentage change in its curved surface area is :
Correct Answer
(B) 3.5% increased
Explanation
Solution: Increase in height = 15% = $$frac{3}{20}$$ Decrease in base radius = 10% = $$frac{1}{10}$$ Initial Final Radius 10 9 height 20 23 Area 200 207 Increment in Area = 207 - 200 = 7 Required % increase in area = $$frac{7}{200}$$ × 100 = 3.5%
[#559] Two numbers are respectively 20% and 50% of the third number. What percent is the first number of the second ?
Correct Answer
(D) 40%
Explanation
Solution: Let the 3 rd number is 100 According to the question, $$eqalign{
& ,{1^{{ ext{st}}}},,,,,,,,,,,,,,,,,,,{2^{{ ext{nd}}}},,,,,,,,,,,,,,,,,,{3^{{ ext{rd}}}} cr
& 20,,,,,,,:,,,,,,,,50,,,,,,,,:,,,,,,,100 cr} $$ Required % = $$frac{20}{50}$$ × 100 = 40%
[#560] 25% of the candidates who appeared in an examination failed and only 450 students qualify the exam. The number of students who appeared in the examination was :
Correct Answer
(B) 600
Explanation
Solution: Percentage of failed students = 25% ∴ Percentage of passed students = (100 - 25)% = 75% According to the question, Total students : = $$frac{450}{75}$$ × 100 = 600