Interview Q&A / Aptitude

1. The average age of 8 men rises by 2 years when two of them, aged 21 and 23, are replaced by two women. What is the average age of the women?

   30 years. The group's total rises by 8 x 2 = 16 years. So the women together are 21 + 23 + 16 = 60 years, an average of 30.

   IntermediateQuick answer1 min read
2. A 40-litre can is full of milk. 4 litres are taken out and replaced with water, and this is done three times in total. How much milk is left?

   29.16 litres. Each operation keeps (40 - 4)/40 = 0.9 of the milk, so after three rounds milk = 40 x 0.9^3 = 40 x 0.729 = 29.16 litres.

   AdvancedQuick answer1 min read