Exactly 3 investors—A, B, and C—invested in a certain business, each for a certain number of months. For these investments, what is the ratio of the profit earned by A to the profit earned by B to the profit earned by C ? (Note: Profit earned is proportional to the product of investment amount and investment duration.)Let's say A, B, and C invested amounts $a, $b, and $c for x, y, and z months, respectively. The question asks for the ratio ax : by : cz.
(1) A invested twice as much as B, and C invested half as much as A and B together.
This implies a = 2b, and 2c = a + b. Substituting a = 2b into 2c = a + b gives 2c = 3b, which simplifies the ratio to 2bx : by : 3bz/2 = 2x : y : 3z/2. Since we know nothing about x, y, and z, this information alone is insufficient.
(2) All 3 investments were for the same number of months.
This implies x = y = z, which simplifies the ratio to ax : bx : cx = a : b : c. However, without knowing the amounts invested, this information alone is insufficient.
(1)+(2) Since from (2) x = y = z, from (1) the ratio becomes 2x : x : 3x/2 = 2 : 1 : 3/2. Sufficient.
Answer: C.