Mathematical questions are tricky. Solving them during exams consumes a great deal of time and focus. Because these math problems are lengthy, we end up making small but disastrous calculative mistakes! So here are a few short cuts and tricks to simplify these calculations:
1. Division tricks
Here’s a quick way to know when a number can be evenly divided by these certain numbers:
• 10 if the number ends in 0
• 9 when the digits are added together and the total is evenly divisible by 9
• 8 if the last three digits are evenly divisible by 8 or are 000
• 6 if it is an even number and when the digits are added together the answer is evenly divisible by 3
• 5 if it ends in a 0 or 5
• 4 if it ends in 00 or a two digit number that is evenly divisible by 4
• 3 when the digits are added together and the result is evenly divisible by the number 3
• 2 if it ends in 0, 2, 4, 6, or 8
2. Multiplication Tricks:
a) Multiplying with 5
To multiply any number with 5 is same as multiplying it with 10 and dividing it by 2. Right? We can use this rule to speed up our multiplication with 5. So here is the trick. Say you want to multiply 236 with 5.
• Divide the number by 2 i.e. 118
• Now add 0 at the end. The answer is 1180
Was that fast math or what! But wait, what if the answer is in decimal? The rule still holds. Try and multiply 1305 with 5.
• Divide the number by 2 i.e. 652.5
• Now multiply it by 10 i.e. 6525. This is same as adding a 0 at the end or moving a decimal point one step to the right.
b) Multiplying with 9
Here is something that comes in handy when multiplying 9 with large numbers, especially if you are fast with subtraction. Say you have to multiply 81 with 9.
• At 0 at the end of the number i.e. 810
• Subtract original number from the new number i.e. 810 – 81 = 729
3. Power Multiplication or Square of a number that ends in 5
Try finding the square of 85 in your head. Takes lot of time right? Now try this fast math trick here.
• Ignore 5 in the units place
• Take the digit in the tens place i.e. 8 and multiply it with its successor i.e.
• 8+1 = 9. Hence, the result of 8×9 is 72
• Simply place 25 at the end of the result i.e. 7225. That’s it! 7225 is the square of 85. That is your answer.
This math trick works with 3 digit numbers too. So the square of 135 is… first multiply 13 with its successor i.e. 14 = 182. Now add 25 at the end. Your answer is 18225. Simple!
Inculcate these small tricks in your daily practice and see how much time and effort they save! More time means less mistakes which means good grades, right? We hope these tricks help you perform better. Best of luck!
Aakash Education Services Limited is now on Telegram. To get all the latest information, tips & tricks, answer solutions for the latest ongoing exams. Subscribe to Aakash on Telegram.
Subscribe to our Youtube channel.
This is incredibly helpful to help my students with divisibility rules.
I also found this rule to test whether 11 is a factor, which you could maybe add to your blog!
Whereas every power of 10 is 1 more than a multiple of 3 (or 9), an alternating pattern emerges for multiples of 11. That is to say, 10 is 1 less than 11, 100 is 1 more than 9×11, 1000 is 1 less than 91×11, 10000 is 1 more than 909×11, and so on. If we write `m11′ as shorthand for ‘a multiple of 11’, we see that odd powers of 10 are m11−1, and even powers of 10 are m11+
Thanks for sharing your valuable feedback. Also, subscribe to our blog http://www.aakash.ac.in/blog and stay tuned for the latest updates.