Quiz: Can You Solve These Multiplication Tables Without a Calculator?: HowStuffWorks
Can You Solve These Multiplication Tables Without a Calculator?
By: Lauren Lubas
6 Min Quiz
Image: Pekic / E+ / Getty Images
About This Quiz
Your math teacher in middle school might have told you over and over again that you wouldn't have a calculator on you at all times as an adult, but he didn't really expect cell phones to challenge that assumption.
If you think you're some form of "Rain Man" level genius when it comes to seeing the answers to math problems in your head, it's time for you to put away the calculator and test your skills. The multiplication problems that you are about to encounter may seem easy at first, but as you work through them, you'll find that they become more and more difficult. You may be able to answer them without a calculator, but only if you know all of the little tricks of multiplication that have been around for years and years. If you don't think you know these tricks, don't worry, we'll share some good ones with you.
If you think you can beat our crack team (who have calculators on them), it's time for you to take this test. Here are 35 multiplication problems to test your skills without a calculating device. Yes, that's right — we expect you to put your phone away as well.
Here's a really, really easy one. 1 x 25 = ___?
Any number multiplied by one is the number itself. Consider multiplication as though it has sets of numbers. In this case, one set of 25 gives you a total of 25. If there were two sets of 25, you'd have a total of 50.
You should be able to do this one in your head. What is 4 x 7?
If you want to multiply anything by four, you can make it simpler on yourself by multiplying the number by two and then doubling the answer. For example, 2 x 7 = 14. 14 doubled is 28, which is the correct answer to 4 x 7.
Can you guess what 8 x 4 is?
All right, if you don't want to use the trick for multiplying by fours, you can always break up the 8. Multiply 4 x 4, which equals 16, then double the 16 to get 32. It's the same as this equation: 4 x 4 x 2 = 32.
Time to double it up. 2 x 33 is what?
When multiplying any number by two, you simply add the number to itself. If you get caught up on two-digit numbers multiplied by two, break up the two-digit number. 3 x 2 = 6, so in this case both numbers are going to end up being 6. 2 x 33 = 66.
Do you know what 8 x 6 is?
If you're having trouble figuring this one in your head, consider splitting the 8 into two 4s. 4 x 6 = 24, plus another 24 makes 48. If it is easier for you to split the 6, you get the same answer: 8 x 3 = 24, plus another 24 makes 48.
You may be able to double numbers, but can you triple them? 25 x 3 = ___?
Multiplying by 3s can be a little tricky. If you get caught up with it, simply multiply the number by two, then add the original number to your answer. For example, 25 x 2 = 50; now add another 25 to get 75. It's the same as this equation: 25 + 25 + 25 = 75.
Here's a somewhat difficult one: what is 9 x 22?
If you are looking for a great way to multiply any number by 9, the best thing to do is multiply that number by 10, then subtract the original number from your answer. For example, 10 x 22 = 220, so subtract 22 from 220 to get 198, which is 9 x 22.
Do you know the trick with 11s? What is 15 x 11?
Multiplying two two-digit numbers can be a little overwhelming, but if you ever see a two-digit number multiplied by 11, there is a weird trick. You add the two digits of the number and then put that result between the two original digits, and you have your answer. (If your answer is greater than 10, carry the 1 to the tens column.) A little confused? Check this out: 1 + 5 = 6, so if you put the 6 between the 1 and the 5, you get 165, which is 15 x 11.
Can you guess what 12 squared is? 12 x 12 = ___?
Always remember: whenever you multiply an even number by an even number, you'll get an even number. To multiply anything by 12, you simply have to multiply it by 10, then add the original number to the answer twice. So, 12 x 10 = 120; 120 + 12 +12 = 144.
71 x 3 equals what?
If you remember the trick with multiplying by 3s, you probably had minimal difficulty with this equation. But if you didn't remember the trick, note that 71 x 2 = 142; 142 + 71 = 213.
Yikes! This one is pretty tough, but we warned you. 9 x 501 = ___?
That triple-digit number might have thrown you off, but the rules for multiplying anything by nine are the same. So multiply 501 by 10 to get 5,010; next, subtract 501 from that answer to get 4,509.
You might have to write this one out by hand, but what is 147 x 8?
It could be a little difficult to figure this one out in your head. There might be several steps involved, including multiplying 147 by 10, then subtracting 147 from the answer twice. To check your work, remember that any number multiplied by an even number must be an even number.
Can you handle all of these fives? 55 x 7 = ___?
The first thing to remember is that if you are multiplying any number by a number that ends in 5, the answer will end in either 5 or 0. It will end in 5 if the number being multiplied is odd, and it will end in 0 if the number being multiplied is even.
This one, you'll definitely need a piece of paper for! What is 82 x 14?
This one is a little tough to do in your head, but you have to break it down a little further. First multiply 82 by 10 to get 820, then multiply 82 by 4 to get 328. Finally, add 820 and 328. If you can't do this one in your head, consider writing it out.
Can you guess what 77 x 82 is?
Whoa, those 82s are getting a little crazy! While you may not be able to do this one in your head, if you figure out that 7 x 82 is 574, you can add 5740 to it, because that is 70 x 82. Once you do that, you add the two products together, and you get 6,314.
Do you know what 62 x 41 is?
This is definitely one that you would have to write out to figure out. The best way to do this is to place the 41 underneath the 62, then multiply the numbers separately, and finally, add them together. That's old school math.
This one is a little tricky. What is 11 x 65?
If you remember the trick to multiplying double digit numbers by 11, you still might have a little bit of trouble with this one; however, the trick works. When you add the two digits of the number that isn't 11 together, if the answer is 10 or more, add the tens column to the first number. In this case, you would add 6 and 5. Since that's 11, add the 1 to 6 in order to get 7 as your first number, so the answer is 715.
25 x 96 might be a little tough, but there is a trick to this one. What is the answer?
Simply looking at this one might overwhelm you, but it's actually not that difficult. With a number so close to 100, you can simply multiply the 25 by 100. Since 96 is 4 less than 100, subtract the product of 4 x 25, which is 100, to get the right answer.
This is getting out of hand now! What is 71 x 53?
A great way to answer this one is to multiply 71 by 50, then multiply 71 by 3, and finally add the results together: 3,550 + 213 = 3,763. If multiplying 71 and 50 seems difficult, consider just multiplying the 7 and 5, then adding two 0s at the end, then adding 50 to that number.
64 x 45 = ___? You might have to guess on this one!
Remember that any number ending in five multiplied by an even number will result in an answer ending in zero. However, for this one, you'll probably have to write out the equation to help you find the correct answer.
There's a trick with 25s ... do you know it? 82 x 25 = ___?
Whenever you're multiplying 25 by anything, consider dividing that number by 4, then multiplying it by 100. For example, 80 divided by 4 is 20, times 100 is 2,000. Then add another 50 and you have your answer: 2,050.
Let's give your poor brain a little break. What is 2 x 64?
When you're multiplying double digit numbers by 2, you should always consider splitting the number up. In this case, 60 x 2 = 120, and 4 x 2 = 8. 120 + 8 = 128. Alternatively, just add the number to itself.
Yes, you can apply the 25s trick to this one, but don't forget that zero! Do you know what 250 x 80 is?
When you multiply two numbers that end in zero, the answer will always end in zero. In this case, you can remove the zeros and multiply 25 by 8, then add two zeros to the end of your answer to get the correct answer.
Break out the pen and paper for this one. Can you answer this equation: 143 x 87 = ___?
Multiplying numbers that are in the triple digits isn't much different than multiplying numbers that have two digits. Put one number underneath the other and multiply them one number at a time. In this case, you should put the two-digit number under the three-digit number to make it go faster.
What is 176 x 12?
Okay, this was a tough one, and we didn't expect you to get it on your own, but there is a trick to it. You can multiply 176 by 10 to get 1,760. Then add 176 to that answer twice. This will give you 2,112.
If you multiply 52 x 74, what answer will you get?
This is another toughy, but if you break up the 52 into 50 and 2, and break up the 74 into 70 and 4, you will find that the answer is easier to come by. However, you might need to write it out to stay organized.
Do you think you know this one? 79 x 11 = ___?
All right, this one involves multiplying by 11. One way to get the answer is to multiply 79 by 10, which makes 790, then add an extra 79, for a total of 869. In math, there's almost always more than one way to arrive at the correct result!
This one looks difficult, but you can figure it out without a pen and paper. 99 x 99 = ___?
Think this one is hard? You could start by multiplying 100 by 99, then be sure to subtract 99 from your answer. That's 9,900 - 99, which is 9,801. Multiplication problems are often easier when you round one of the factors up or down, then adjust your answer accordingly.
Break it up, and you might have an easier time. What is 38 x 70?
To make this one a little easier on you, start by removing the 0 from 70. Then multiply 7 by 38. However, you must remember to add the zero at the end of your result, or you'll be way off.
41 x 22 is what?
A great way to answer this question is to multiply 41 and 11 twice. If you remember the trick with the 11s, you'll know right away that 41 by 11 is 451; add another 451 and you get your answer, which is 902.
All right, time for a brain break (kind of). Do you know what 85 x 2 is?
You know that any number ending in five multiplied by an even number will have a product that ends in zero. A great way to solve this particular problem is to multiply 80 by 2, then multiply 5 by 2, and finally, add your results to get 170.
Do you think you can guess the answer to 74 x 3?
Don't forget that when you're multiplying numbers by 3, it's always a good idea to multiply the number by two then add the number to your results. 74 x 2 = 148; 148 + 74 = 222. Another way to find the answer is to multiply 75 by 3, making 225, then subtract 3, making 222.
What is 51 squared? 51 x 51 = ___?
Whoo, this might seem a little difficult at first, but if you multiply 50 and 51, you get 2,550, and don't forget the other one that was involved. Add another 51 to that answer, and you'll get the correct answer, 2,601.
The triple digits might scare you a bit, but don't be fooled. What is 24 x 685?
If you did this one on your own, without even a scrap of paper, we are impressed. This is a difficult equation, but in the end, we know it ends in zero. We can use the properties of multiplying by 25; however, we'd have to subtract 685 from 17,125 to get the answer, which is 16,440.
This is a heavy one. What is the product of 72 x 23?
This one isn't as hard as it might look. Consider multiplying 72 by 20, which makes 1,440. Next, multiply 72 by 3, which makes 216. Add your results, 1,440 + 216, and you will have the correct answer, 1,656. If you're having trouble with those numbers, you can use the secret to multiplying by 3s to help you.
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