ASVAB Math Tricks - Multiplying Numbers That End In Zero

If you are studying for the math portion of your upcoming Armed Services Vocational Aptitude Battery or ASVAB exam, you will likely be faced with many mathematical calculations that at first glance appear to require either a calculator (which is not allowed) or a long hand-written form of calculations to get the answer. My goal is to show you, not only how to simplify the math process, but also to show you a few mathematical tricks. In particular, this article will focus on multiplying numbers that end in zero

If you are faced with an ASVAB style question that asks you to multiply two medium or large numbers, for example 22 times 37, you may find yourself wasting too much time with pen and paper. If instead you simplify the numbers to the point where your calculations are significantly shorter, you will find that you have more time to complete both the Mathematics Knowledge (MK) and Arithmetic Reasoning (MR) sections

Take a look at your most recent sample exam practice problems and answer choices. Look at the answer choices given. The numbers provided are not so close to each other that a perfectly accurate calculation is required. Instead the numbers will be far enough apart that even with a few rounding and estimations your answer will still be close enough to just one of the answer choices.

With the above example, instead of calculating 22 times 37 the long way, we can round each number to the nearest unit of 10. Since 22 is very close to 20 we round it down. And 37 is very close to 40 so we round it up.

Now we have a new example that reads 20 times 40. Once again you have the option to calculate these the long way, which will still be faster or you can take this one step further and actually do the math in your head

How?

Isn’t the number 20 really just 2 times 10? And isn’t the number 40 really just 4 times 10? If we think of two digit numbers ending in zero as the number times 10, we can simply these problems from requiring a calculator, to not even needing pen and paper

Instead of 20 times 40 we now have a problem that reads 2 times 10 times 4 times 10. Multiplication allows us to rearrange the order of the numbers, so let’s look at this example as 2 times 4 times 10 times 10.

Doesn’t this suddenly look so much simpler? 2 times 4 is 8, and 10 times 10 is 100. That leaves you with 8 times 100 which is 800.

The actual answer for 22 times 37 is a very close 814. Since the ASVAB won’t give you choices too close to the actual answer, 800 will still be the closest value. Was it worth doing all that extra math for a difference of 14?