DS - 10% and 6%

it should be D

Xbond wrote:Hi there,

Could you explain in the simplest this concept and how to resolve it


Part of the $10,000 are invested to a certain account at 10% simple annual interest rate, and the
remainder are invested to another account at 6% simple annual interest rate. How much are
invested to the 10% rate account?

(1) At the end of the first year, the total interest rate is $600
(2) The amount invested to the 10% account is 1.8 times that invested to the 6% account.

Step 1 of the Kaplan Method for DS: focus on the question stem.

We want to determine the amount invested at 10%... let's call that "x".

Since we're investing a total of $10000, the amount invested at 6% is the remainder: "10000-x".

Accordingly, we can set up an equation:

10%(x) + 6%(10000 - x) = interest earned per year

Step 2 of the Kaplan Method for DS: consider each statement by itself.

(1) Interest for the first year is $600.

Perfect! We can substitute 600 into the right side of our equation to get:

10%(x) + 6%(10000 - x) = 600

We now have 1 variable and a bunch of numbers, we can solve for x: sufficient.

(2) Since the amount invested at 10% is x and since the amount invested at 6% is (10000-x), we can use this info to set up another equation:

x = 1.8(10000 - x)

1 variable and a bunch of numbers, we can solve for x: sufficient.

Step 3 of the Kaplan Method for DS: if necessary, combine.

Not necessary to combine, since at least 1 statement was good enough alone!

Each of 1 and 2 is sufficient alone: choose (D).