18 Math Hacks To Make Your Life Infinitely Simpler

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mattstaff
Apr 30, 2018 8:00 PM EDT

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  • 01
    Text - 64% 80% 879 To calculate the percentage of a number (that isn't 10%) just find 1% first and then multiply it. 96% 7% 93% 0% % So, for example, 3% of 528 would be 528*.01 5.28 (move the decimal two places left). Now just multiply by 3to get 15.84. 94% 98% 60 50% 97% 93% 62% 16% 93% 97% 92% 51% 64 58% 64%
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  • 02
    Text - To figure a tip just move the decimal one place to the left in order to get 10%. Then either add half of what you have left to get 15% or double it for 20% For example, if the bill is $45.35 then $4.54 is 10% Half of $4.54 is $2.27 so if you want 15% just add that on. It would give you $4.54 + $2.27 $6.81. Getting 20% is even easier because you just double it. $4.54x2 = $9.08.
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  • 03
    Games - To calculate your annual salary.just take your hourly wage, double it, and add 3 zeros. Let's say you are making $15 per hour. Just double that for $30 and then add three zeros for $30,000.
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  • 04
    Text - For squaring numbers, one possible trick is to add/subtract from the number until you get two numbers you can easily multiply. Then add the difference of the number you added/subtracted. To give an example, 46 squared could be 42x50 because 46- 4 = 42 and 46 4 50. So 42x50 would be 2100. Now square the number you added/subtracted so 4 squared 16. Now add 16 to get 2116.
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  • 05
    Text - To figure out an approximate square root, do the following: find the next lower perfect square. Add it to your number. Now divide by the square root of the lower perfect square. And now divide again by 2. For example: Take 31. The next lowest perfect square is 25, So 31 plus 25 is 56. Now divide by the square root of 25. So 56/5 11.2. Now divide by 2 to get 5.6.
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  • 06
    Text - To see if a number is divisible by three, add up the digits. If the sum is divisible by three, so is the number. For example: 354 is 3+5+4=12 Note: this also works for 9.
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  • 07
    Text - To convert miles to kilometers, you can get a pretty good estimate by adding 60% The best way is to add 50% and then 10%. For example: 60 miles in km would be: 60x0.5 = 30 and 60x0.D- 6. Now, 30 +6 36. Add this to 60 to get 96 km. To go from kilometers to miles, just/subtract 40%3 To make it easy, just cut in in half, and add 10%. So to get 350 km in miles su btract half of 350. That gives you 175. Now add back 10% of 350 which is 35. This leaves you with 210. 0 220 H0889 ODO
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  • 08
    Text - F C 50 To approximate conversions between Celsius and Fahrenheit just multiply by 2 and add 30 |(going from C to F). Do the reverse to go from UGI F to C (subtract 30 and divide by 2). 30 20 80
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  • 09
    Text - To check if a number is divisible by 6 you need to combine two divisibility rules (twos and threes). If it is divisible by both 2 and 3 then it is divisible by 6. Check out the earlier hack about dividing by 3, and you should know that all even numbers are divisible by 2.
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  • 10
    Text - ננממ You can multiply by rounding. This works especially well if one of the numbers is already nice and round (ends in O). Just round off the other number, multiply, and adjust the result accordingly. For example, if you want to calculate 18 30, just do 20*30 which is 600 and then subtract two 30s for 540. S15151515 1S1S1S1LLLL
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  • 11
    Cash - 5566320 G 7 SYSTE THIS NOTE FOR ALL DER IS L The rule of 72: 72 divided by the interest rate will give you a rough estimate of how many years it would take to double your money. 93 A RAL OLLAR kiciolcielcio STAIES LEAL REST FEDERAL R HC 38553 DOL 3ONTONSn SI 31ON Y S IVISOUINO RESER SIH1 C3 ahane Ceatede Cahal
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  • 12
    Text - Whe es to percentages, remember that x% of the same as y% of x. This means that if 2% of 50 is too hard to figure out, you can just flip it - 50% of 2.That's a lot easier.
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  • 13
    Text - To square any double digit number that ends in 5, just put 25 at the end and multiply the first number by the following digit. So, for example, 45 squared would be 2025 because 5 is the next digit above 4 so 4x5 = 20. Now just put a 25 on the end for 2025. NORTH
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  • 14
    Text - To multiply a 2 digit number by 11 just add the digits together and stick the answer between them. For example 42x11 would be 4 2 6 Now put the 6 between the 4 and the 2 to get 462. If the answer is 2 digits, carry the one. For example 58x11 would be 5+8=13. Just add the one to the 5 to get 638.
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  • 15
    Font - 759 To do mental addition, it's much easier to work from left to right rather than the way you do on paper (right to left). For example, to do 376+581, add 300 +500 to get 800. Now add on 70+80, which is 150. This brings the total to 950 Then add on the 7 to Basically, break the addition down'into smaller parts from left to right. Set 957
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  • 16
    Text - 759 For mental subtraction, the idea is similar to addition. Work left to right, but there's some rounding involved. Let's go with 632-487. First add 3 in order to round 487 up to the nearest 10, so 490. Now, the problem becomes 632 - 49o. This is much easier. 632 - 400 is 232. Now subtracting 9o you get 142 (it's 10 more than subtracting 100). From there, just remember to add back the 3 from the beginning. This gives you 145.
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  • 17
    Text - If you need to multiply a number by 5 it may be easier to half it and then multiply by 10. For example, 315*5 would be 315/2 = 157,5 Now just move the decimal over to multiply by 1o and get 1575.
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  • 18
    Pool - To see if a number is divisible by 8, check the last three digits. If they are divisible by 8, then the number is divisible by 8. For example, 3,423,024 would be divisible by 8 because 024/8 3
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