There are some people for whom math is as simple as the alphabet. Then there’s the rest of us who sit staring in envy, trying to figure out what 17 plus 5 equals without counting on our fingers. If you’re not one of the numerically-inclined, getting better at math can seem hopeless.
But luckily for us, there are some simple tricks out there to help us get better at math! Read on to learn some ways to improve your mental math game.
Think About Things in Tens
One quick way to get better at mental math is to think about everything in terms of tens. This works especially well for addition and subtraction. Let’s say, for example, that you want to add 736 and 287 without using a calculator or Googling “math tutor near me.”
Start by pulling the 6 and the 7 off each number, so now you have 730 and 280. If you like, you can reduce those numbers to 73 and 28, making their total 101, or 1,010 with the last 0 added back on. Now add the 6 and the 7 together (13), and add that number to the total, giving you 1,023 as the answer.
Subtracting from 1,000
Subtracting numbers from 1,000 may seem like an impossible task to do in your head, but with the right trick, you can do it in a snap. You’ll want to separate the number you’re subtracting into its digits and subtract each digit from nine and the last one from ten. Let’s use the example of subtracting 384 from 1,000.
So the first thing you’ll want to do is subtract 3 from 9, giving you 6, and 8 from 9, giving you 1. Then subtract 4 from 10, giving you 6, and combine the numbers back together. So, 1,000 minus 384 is 616.
Multiply by Five
Most people know their five times tables, but most of us only know them up to 12 (thanks, analog clocks). What happens if you need to multiply 5 by a larger number, though – for example, 5 times 28? The trick is to divide the number by 2 and then add 0 to the end.
So in our example of 5 times 28, we’re going to start by dividing 28 by 2, giving us 14. Then we’ll add the 0 back onto the 14, which makes the answer to 5 times 28 equal 140. This works with any number because 5 is half of 10, and multiplying numbers by 10 is easy.
If it’s easier for you, you can also do this trick the other way around. Take the number you’re multiplying by, add a 0 to the end, and then divide it in half. So in our example, we would make 28 into 280 and then divide 280 by 2, giving us 140.
Multiply by Nine
While most of us do know our five times tables, many of us may not remember our nine times tables any more. Trying to remember what 9 times 7 is on the fly can be a problem. Luckily, you have a trick to remember those times tables on hand – literally.
Hold up both hands in front of you with your fingers spread out. Then take whatever number you’re multiplying by and count across to that finger, and put it down. The number of fingers on either side of your hidden finger makes the answer.
So let’s use our 9 times 7 math problem. Count across to your seventh finger from the left in this case, the index finger on your right hand) and put it down. You have six fingers, the break, and then three fingers, meaning the answer to 9 times 7 equal 63.
Multiply by Eleven
Multiplying by 10 is easy (you just add a 0 to whatever number you’re working with), but multiplying by 11 is a problem. In the single digits, this is easy because you just double the digit (3 times 11 is 33). But there’s a simple trick that can help you multiply 11 by larger numbers as well.
Let’s say you need to multiply 11 by 63 in a hurry. The first step is to separate the digits of 63. Then you’re going to add the 6 and the 3 together to get 9. Place the nine in between the six and the three to get the answer; 11 times 63 is 693.
If you’re adding numbers that come up to a two-digit number (for example, 11 times 87), there is one more step to this trick. In this example, you add 8 and 7 to come up with 15; you’re going to put only the second number in the middle (857). Then you’re going to add the 1 to the first number to come up with a final answer of 957.
Find a Percentage
Trying to find a percentage quickly can be a pain, even if you happen to have a calculator on hand. If you’re working with whole numbers, there’s a quick multiplication trick you can use. Even if you aren’t working with whole numbers, this is a good way to get a quick estimate.
You’ll want to multiply the number you have and the percentage you want and then move the decimal point over two places. So, for example, let’s say you need to find 30 percent of 60. You know 30 times 60 is 1800, which makes 30 percent of 60 equal to 18.
If you aren’t working with whole numbers, the important thing is to remember your rule of tens again. So if you have to find 20 percent of 395, you’ll want to start by getting 10 percent of that number (39.5). To get 20 percent, double that number, making 20 percent of 395 equal to 79.
Now let’s say you’re trying to average a lot of numbers (grades, for example) and figure out how to change that final average. For example, let’s say you’ve gotten a 78, an 85, a 97, a 93, and an 88 in a class and you want to get a 90 average. This trick will help you figure out what grade you need to get on your final exam.
You’ll want to start by finding the difference between each of the numbers and your target final. So in this case, you would have -12, -5, 7, 3, and -2. Add those numbers together (-9), and you know how much to add to your target average. If you want to get an A in that class, you’re going to have to make a 99 on the final.
Learn More Ways to Get Better at Math
Mental math can be a pain for some of us, but if you remember these tricks, it doesn’t have to be. The biggest tip is to think about everything in tens. If you want to get better at math, the trick is at your fingertips — all ten of them.
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