Interview Q&A / Aptitude
Aptitude interview questions
Quantitative shortcuts for placement tests: percentages, time and work, and more.
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- A sum at compound interest amounts to ₹6,050 in 2 years and ₹6,655 in 3 years. Find the rate and the principal.
Rate = 10% and principal = ₹5,000. The third year's interest is 6,655 - 6,050 = ₹605, which is 10% of ₹6,050. Then P = 6,050 / (1.1)^2 = 6,050 / 1.21 = ₹5,000.
IntermediateQuick answer1 min read - What is the rule of 72, and how long does money take to double at 9% compound interest?
Doubling time is roughly 72 divided by the annual rate in percent. At 9% that is 72 / 9 = 8 years. The exact answer is log 2 / log 1.09, about 8.04 years, so the rule is very close.
IntermediateQuick answer1 min read