With all of the cancelled sporting events and schools being closed in an attempt to slow the spread of COVID-19, better known as the coronavirus, now is a great time to step up your GMAT prep time. After all, all you need to study is a computer and a desk!

This week, President Donald Trump said that travel between the United States and Europe would be halted for the next 30 days as an effort to stop the spread of the coronavirus.

So, in order to keep your brain busy over the next 30 days, I’m going to publish one practice Data Sufficiency question each day! You can choose to do all of them, or none of them.

Click on the tag “Social Distancing DS Challenge” at the bottom of this post to see all of the questions in this series!

And remember to take whatever precautions you need to stay healthy over the next few weeks!

**Question #1**

How much is 10 percent of a number?

(1) 20 percent of the number is 40.

(2) 50 percent of the number is 100.

**Explanation**

Either of the given statements is sufficient because with each one we can figure out the mystery number (and so we can easily find 10 percent of the mystery number). For example, if we know 50 percent of a number is 100 — then all we have to do is double it to find the mystery number of 200. The same goes for knowing that:

20% = 40: (^{20}/_{100}) * (mystery number) = 40

mystery number = 40 * (^{100}/_{20}) = 200.

The trick here is to avoid actually *doing out *the math. As long as you know that the information given in each statement *is sufficient* to calculate the answer, select the appropriate answer choice (and remember: the answer choices never change in data sufficiency), then move on. Data sufficiency questions are about just that: the sufficiency of the data. They’re not about calculations. The correct answer is (D).

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