Articles by Rich Zwelling
Is That Number Prime?
Rich presents the easiest way to figure out if a number is prime or not.
Be Careful When Interpreting “Must Be True” Questions
Rich must be true to himself and share this advice with you.
The Speedy Road to Insufficiency
Should you prove that statements are sufficient or should you prove them insufficient?
Intuition and Common Sense on Geometry DS Questions
Who cares about the value of x? Well, on DS, we don't!
The AWA Isn’t That Important… So Can I Blow It Off?
Should you sacrifice the AWA for a well-rested mind later on? Rich provides his opinion on this stategy.
Tips for Comparing Fractions on the GMAT
Fractions, always a headache! Use Rich's tips to navigate through all the signs and powers.
Filling in Your Chart: A Data Sufficiency Primer
Rich breaks down an overlapping sets question, complete with tables to visualize the solution!
To Venn or Not to Venn? Depends on the Question
Should you go for Venn diagrams or tables? Both require you to showcase your drawing skills, but most of the time one is quicker than the other.
Two Shortcut Formulas for Set Problems
If you're one of those people who goes crazy over overlapping sets problems, this post is for you.
More Fun with Weighted Averages
Weighted averages are really useful for Data Sufficiency, but they're not too bad for Problem Solving either.
What the Heck is a Weighted Average?
You can bet that weighted average questions will show up in Data Sufficiency!
Quick Mental Math: Averages
If the GMAT is more about reasoning than speed calculations, then why am I writing a post on quick mental math?
How to Approach Rate Problems on GMAT Quant, Part II
A handy Knewton guide to solving work rate problems.