The I.Q. of a twelve-year-old student, Sohan, is 75. What will be his mental age in years?

Under the Life Cycle Hypothesis, a person starts working at age 25, retires at age 65, and expects to die at age 75. He has no initial wealth and earns ₹6,000 per year during his working life. Assuming he consumes his income uniformly over his entire lifetime, what is his Average Propensity to Consume (APC) during his working years?

A laptop, a tablet, and a mobile phone have their present ages in the ratio 5:7:4. After 4 years, the average age of the laptop and the tablet will be 2 less than twice the present age of the mobile phone. What is the average of their present ages?