Here’s GMAT Quant/Math Batch #3 from our friends at Target Test Prep . Throw these problems into your GMAT prep mix to increase your chance of breaking into scores of 680-750 and above. And don’t just go through the problem, really seek to understand the underlying rules and relationships that lead to a solution.

Here you goes:

**PRACTICE PROBLEM 3A**

If 5^{x} – 5^{x-1} = 500 , what is the value of (x – 1)^{2}?

(A) 1 (B) 4 (C) 9 (D) 25 (E) 36

**Solution:**

We should recognize that we have subtraction of bases with exponents. This means before we can combine the equation’s terms, we need to factor out.** **However, to help see what we can factor out, we can rewrite the equation.

5^{x} – 5^{x-1} = 500

5^{x} – (5)^{x}(5)^{-1} = 500

Now we can easily see to factor out the common term of 5^{x}. We now have:

5^{x} – (5)^{x}(5)^{-1} = 500

5^{x} (1-5^{-1}) = 500

5^{x} (1-1/5) = 500

5^{x} × 4/5 = 500

Our next step is to break down all the values into prime factors. This will make canceling out much easier.

Finally, we have to solve for (x – 1)^{2}, so (4 – 1)^{2} = 3^{2} = 9

**Answer: C**

** **

**PRACTICE PROBLEM 3B**

If x is an integer and -2x + 1> 7, what is the value of x?

1) x^{2} + 9x + 20 = 0

2) x ≥ -4

**Solution:**

**Question Stem Analysis:**

Begin by simplifying the information given in the stem.

-2x + 1 > 7

-2x > 6

x < -3

We’ll use this information in conjunction with the statements that follow.

**Statement One Alone:**

x^{2} + 9x + 20 = 0

Solve the above equation:

x^{2} + 9x + 20 = 0

(x+4)(x+5) = 0

x = -4, x = -5

From the information given in the stem, x < -3. Since both -4 and -5 are less than -3, statement one alone is not sufficient to give us one value for x.

Eliminate answer choices A and D.

**Statement Two Alone:**

x ≥ -4

Since the only integer value of x that is less than -3, as required by the stem, and greater than or equal to -4 is -4, we have a single value for x. Statement two alone is sufficient.

**Answer: B**

For more GMAT Help, go here.

June 5, 2013 at 2:57 AM

Hey ! in 3B .. second statment tells us that x >= 4 not -4 , is that correct ?

June 5, 2013 at 10:48 AM

you’re right Suhail! I’ve changed that typo.

June 5, 2013 at 3:56 AM

Thanks! could solve the DS….would like to know something. I have not yet reached the 650 mark in my tests..what do I do? how do i do? what am i NOT doing? I dont get it😦

Also, in Verbal, I am often short of time and guess work the last 5-6 Q. How do i improve on that? In general how do i manage my time in both quant and verbal?

Cheers!

June 5, 2013 at 8:23 AM

Hello Samheeta. You may want to send info to http://www.mbaover30.com/gmat-help/and see what advice the Target Test Prep folks have for you.