Math is the subject unworthy being neglected in school If you have slept for all math lessons do not despair It’s never too late to catch up and even surpass their peers We have collected the best mathematical techniques that can be useful in everyday life Use these 5 math lifehack tips to make your life easier:
#1 How to calculate percentages quickly 
The method works if both numbers end with zero Remove the last digit from number which you want to get a percentage and from percentage and multiply the resulting numbers on each other:
40% of 300 = 12%
4 ? 30 = 120 => 12%
#2 Japanese Multiplication
The essence of the reception is to draw straight lines and counting the intersections between them. You can read my article about Japanese Multiplication here.
#3 Multiplication by 9
This rule for multiplying any number from 1 to 9 by 9 When multiplying a number by 9 subtract 1 from this number and assign a number which gives 9 when it’s combined with the first one:
3 ? 9 = 27
27 = (3-1) + (9 -(3-1)) = 2 + 7
#4 How to compare the dates and days of the week quickly
Each month contains a day of the week which falls on a multiple of 7 You just need to remember in which months this day is Monday Tuesday and so on So you’ll remember months under the names “Mondays in December” or for example “Thursdays in August” Then you can quickly compare the dates and days of the week in the near future.
– Let’s meet in June say the 15th of?
– No it’s “Saturdays in June” and thus the 15th – this Sunday I’ll be out of town and unavailable.
#5 Butterfly Fractions
To add or subtract fractions the butterfly way:
1. Write the fractions side-by-side as usual and draw two wings along the diagonals made by the numerator of one fraction and the denominator of the other fraction and draw an antenna on each wing.
2. As suggested by the wings that look like a multiplication sign multiply the numbers in each wing and put the product in the antenna for the wing.
3. To give your butterfly a body connect the bottom parts of the wings with a body-like loop and multiply the two denominators it connects putting the product inside the body.
4. Add or subtract the numbers in the antennae in keeping with what is being done to the fractions and put the result over the number in the body.
5. If necessary reduce or simplify the result.
The butterflies above for 3/4 + 2/5 and 3/4 – 2/5 illustrate the procedure The only difference in subtracting the fractions versus adding them is in the last step where the numbers in the antennae are subtracted instead of added.
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