From May 1 to May 30 in the same year, the balance in

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From May 1 to May 30 in the same year, the balance in a checking account increased. What was the balance in the checking account on May 30?

(1) If, during this period of time, the increase in the balance in the checking account had been 12 percent, then the balance in the account on May 30 would have been $504

(2) During this period of time, the increase in the balance in the checking account was 8 percent.

[spoiler]OA=C[/spoiler]

Source: GMAT Paper Tests

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by Vincen » Sun May 05, 2019 1:33 pm

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Hi Gmat_mission.

In this DS question, all we need to see is if we are able to find the balance in the checking account on May 30. Let's take a look at the statements.

Statement 1:
(1) If, during this period of time, the increase in the balance in the checking account had been 12 percent, then the balance in the account on May 30 would have been $504
First, notice that this statement tells us the balance on May 30. But this is just a supposition. So, actually, we don't know what is the balance on May 30.

Here, we could find what was the balance on May 1, but we don't know what is the actual percent increase. Therefore, this statement is NOT SUFFICIENT.

Statement 2:
(2) During this period of time, the increase in the balance in the checking account was 8 percent.
Now, we are told the actual percent increase, but we don't know how much money was in the account on May 1, so we can't determine what is the balance on May 30. Therefore, this statement is NOT SUFFICIENT.

Statement 1 + Statement 2:
(1) If, during this period of time, the increase in the balance in the checking account had been 12 percent, then the balance in the account on May 30 would have been $504
(2) During this period of time, the increase in the balance in the checking account was 8 percent.
Using the first statement, we can know how much money was in the account on May 1.

Let \(I\) be the balance in the checking account on May 1. Here, we are told that $$I+12\%\cdot I=504\ \ \ \Rightarrow\ \ 1.12I=504\ \ \Rightarrow\ I=450.$$ On the other hand, the second statement tells us that the increase was 8%, so on May 30 there will be
$$Final=I+8\%\cdot I=450+8\%\cdot450=450+36=486\ dollars$$ Therefore, using both statements together is SUFFICIENT.

Hence, the correct answer is the option _C_.

I hope it helps you. <i class="em em-sunglasses"></i>

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Gmat_mission wrote:
Sat Apr 27, 2019 3:07 am
From May 1 to May 30 in the same year, the balance in a checking account increased. What was the balance in the checking account on May 30?

(1) If, during this period of time, the increase in the balance in the checking account had been 12 percent, then the balance in the account on May 30 would have been $504

(2) During this period of time, the increase in the balance in the checking account was 8 percent.

[spoiler]OA=C[/spoiler]

Source: GMAT Paper Tests
Solution:

Question Stem Analysis:


We need to determine the balance in the checking account on May 30.

Statement One Alone:

We see that the beginning balance (i.e., the balance on May 1) of the checking account was 504/1.12 = $450. However, since we don’t know the actual percent increase in the balance, we can’t determine the balance in the account on May 30.

Statement Two Alone:

Since we don’t know the balance of the checking account on May 1, even if we know the percent increase in the account, we can’t determine the balance in the account on May 30.

Statements One and Two Together:

Since we know both the beginning balance of the checking account ($450) and the percent increase during the month (8%), we can determine the balance of the account on May 30 to be 450 x 1.08 = $486. Both statements together are sufficient.

Answer: C

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