Mathematics/General Ability MCQs
Topic Notes: Mathematics/General Ability
MCQs and preparation resources for competitive exams, covering important concepts, past papers, and detailed explanations.
Plato
- Biography: Ancient Greek philosopher (427–347 BCE), student of Socrates and teacher of Aristotle, founder of the Academy in Athens.
- Important Ideas:
- Theory of Forms
- Philosopher-King
- Ideal State
171
The price of a commodity is reduced by 25%. How much percent must a family increase consumption so the expenditure remains the same?
Answer:
33.33%
If price decreases by R%, required increase in consumption is (R / (100-R)) * 100. Here, R = 25. Increase = (25 / 75) * 100 = (1/3) * 100 = 33.33%.
172
The price of sugar increases by 20%. By what percent should consumption decrease so the expenditure remains the same?
Answer:
16.66%
If price increases by R%, required decrease in consumption is (R / (100+R)) * 100. Here, R = 20. Decrease = (20 / 120) * 100 = (1/6) * 100 = 16.66%.
173
A number is increased by 10% and then decreased by 10%. The net change is?
Answer:
1% decrease
Let the number be 100. Increased by 10% makes it 110. Decreased by 10% makes it 110 - (10% of 110) = 110 - 11 = 99. The net change from 100 to 99 is a 1% decrease. (Rule: net change = -x^2/100 = -100/100 = -1%).
174
Two numbers are respectively 20% and 50% more than a third number. The first number is what percent of the second?
Answer:
80%
Let the third number be 100. The first number is 120 and the second number is 150. The first as a percent of the second is (120 / 150) * 100 = (4/5) * 100 = 80%.
175
If A is 50% larger than C and B is 25% larger than C, then A is what percent larger than B?
Answer:
20%
Let C = 100. Then A = 150 and B = 125. The difference between A and B is 25. A is larger than B by (25 / B) * 100 = (25 / 125) * 100 = 20%.
176
If A's salary is 25% more than B's, then B's salary is what percent less than A's?
Answer:
20%
Let B's salary be 100. Then A's salary is 125. The difference is 25. To find what percent B is less than A, compare the difference to A's salary: (25 / 125) * 100 = (1/5) * 100 = 20%.
177
What is 25% less than 80?
Answer:
60
25% less than 80 is 75% of 80. 0.75 * 80 = 60. Alternatively, 25% of 80 is 20, and 80 - 20 = 60.
178
What is 20% more than 50?
Answer:
60
20% of 50 = (20/100) * 50 = 10. To find 20% more than 50, add this value to 50: 50 + 10 = 60. Alternatively, 1.2 * 50 = 60.
179
A number decreased by 15% becomes 170. Find the number.
Answer:
200
Decreasing a number by 15% means it becomes 85% of its original value. 85% of x = 170. 0.85x = 170. x = 170 / 0.85 = 200.
180
A number increased by 20% becomes 120. The number is?
Answer:
100
Let the number be x. Increasing x by 20% gives 120% of x. So, 1.2x = 120. Solving for x gives x = 120 / 1.2 = 100.