CAT 2020 Slot 1 QA Q3 Interest

Question 3 of the Quantitative Ability (QA) section, CAT 2020 Slot 1, with CAT's official answer and a worked solution.

Veeru invested Rs 10000 at 5% simple annual interest, and exactly after two years, Joy invested Rs 8000 at 10% simple annual interest. How many years after Veeru’s investment, will their balances, i.e., principal plus accumulated interest, be equal?

TITA: type in the answer. There are no options and no negative marking.

Answer: 12 Interest TITA

Solution

t years after Veeru invests: Veeru has \(10000+500t\); Joy has \(8000+800(t-2)\).
\(10000+500t = 6400+800t \Rightarrow 300t = 3600 \Rightarrow t=12\).