Problem Solving

Hi All,

When a GMAT question presents what appears to be a 'step heavy' calculation to you, it's important to remember that the Quant section of the GMAT is NOT a 'math test'; it's a 'critical thinking' test that requires lots of little calculations as you work through it. Here, while it may be temping to try to perform each individual calculation, you should note the patterns involved in the work.

Notice that while you 'subtract 1/3' early on, you would then 'ADD 1/3' in the next step, so those two calculations 'cancel out.' The same cancellation occurs with the two 1/4s and so on. Thus, you're ultimately left with 1/2 - 1/6....
1/2 - 1/6 =
3/6 - 1/6 =
2/6 = 1/3

Final Answer: C

GMAT assassins aren't born, they're made,
Rich

BTGmoderatorDC wrote:$$\left(\frac{1}{2}-\frac{1}{3}\right)+\left(\frac{1}{3}-\frac{1}{4}\right)+\left(\frac{1}{4}-\frac{1}{5}\right)+\left(\frac{1}{5}-\frac{1}{6}\right)=$$

$$A.\ -\frac{1}{6}$$
B. 0
$$C.\ \frac{1}{3}$$
$$D.\ \frac{1}{2}$$
$$E.\ \frac{2}{3}$$

If we remove the parentheses, it is easy to see that all the terms except the first and last are cancelled. So we are left with

1/2 - 1/6 = 3/6 - 1/6 = 2/6 = 1/3

Answer: C