Aptitude interview questions and quick answers
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01If A's salary is 20% more than B's, by what percentage is B's salary less than A's?
B's salary is 16.67% (1/6) less than A's. If B earns 100, A earns 120. The gap of 20 is measured against A's 120: 20/120 = 1/6 = 16.67%.
Read the full explanation02A 60-litre mixture has alcohol and water in the ratio 2 : 1. How much water must be added to make the ratio 1 : 2?
60 litres. The mixture has 40 L alcohol and 20 L water. Alcohol stays 40 L, and for 1 : 2 water must be 80 L. So add 80 - 20 = 60 litres of water.
Read the full explanation03Rohan's age 6 years from now will be 5/3 of his age 6 years ago. What is his present age?
24 years. If his age is x, then x + 6 = (5/3)(x - 6). So 3x + 18 = 5x - 30, giving x = 24. Check: 30 is 5/3 of 18.
Read the full explanation04The sum of the ages of 5 children born at intervals of 3 years each is 50 years. What is the age of the youngest child?
4 years. If the youngest is x, the others are x + 3, x + 6, x + 9 and x + 12. So 5x + 30 = 50 and x = 4. The ages are 4, 7, 10, 13 and 16.
Read the full explanation05Ten years ago, A was half as old as B. If the ratio of their present ages is 3 : 4, what is the sum of their present ages?
35 years. Present ages 3x and 4x. Ten years ago: 3x - 10 = (4x - 10)/2, so 6x - 20 = 4x - 10 and x = 5. Ages are 15 and 20.
Read the full explanation06In what ratio should rice costing ₹40 per kg be mixed with rice costing ₹55 per kg to get a mixture worth ₹45 per kg?
2 : 1. By alligation, cheaper : dearer = (55 - 45) : (45 - 40) = 10 : 5 = 2 : 1. Check: 2 kg at ₹40 plus 1 kg at ₹55 costs ₹135 for 3 kg, which is ₹45 per kg.
Read the full explanation07What is a common pitfall related to "If A's salary is 20% more than B's, by what percentage is B's salary less than A's"?
Answering 20% for both directions.
Read the full explanation08How would you explain "If A's salary is 20% more than B's, by what percentage is B's salary less than A's" in an interview?
"The base flips. With B as 100, A is 120, and B is 20 less out of 120, so 16 and two thirds percent less. The quick formula is r over 100 plus r."
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