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Math tricks
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Feb 25, 2025
0
#3
Rules of divisibility (pls give me any more you know of):
2: the last digit is 2,4,6,8, or 0
3: the sum of all the digits is divisible by three (1935=1+9+3+5=18, 18 is divisible by three, so 1935 is as well)
4: last two digits are divisible by 4 (183846484649464732 is divisible because 32 is divisible)
5: last digit is 5 or 0
6: divisible by 2 and 3
7: thank you, @stixystix0212, for helping with this one.
double the last digit of the number. Then subtract from the other digits. Repeat until you get a number that is divisible by 7 or you get 0
(161, 16-1•2, 14 is divisible.)
8: last three digits divisible by 8 (2737479464487120 is divisible because 120 is divisible)
9: the sum of all the digits is divisible by nine (1935=1+9+3+5=18, 18 is divisible by nine, so 1935 is as well)
10: last digit is 0
Feb 25, 2025
0
#4
To find the "hypotenuse" of an ellipsoid, which is essentially the longest possible distance across the ellipsoid, you need to identify the semi-axis with the greatest length, and simply double that value, as the "hypotenuse" in this context refers to the length of the major axis of the ellipsoid; the formula for an ellipsoid is: x²/a² + y²/b² + z²/c² = 1, where "a" represents the length of the semi-major axis (longest), "b" the semi-intermediate axis, and "c" the semi-minor axis; therefore, the "hypotenuse" would be 2a.
Feb 25, 2025
0
#5
Back in my day we cheated with good old hand-written notes
Use the latitude longitude button on your scientific calculator to find hours and seconds in a given time, can be quite useful for physics
Hours and minutes my bad
OneThousandEightHundred18 wrote:
Back in my day we cheated with good old hand-written notes
That wouldn’t work. My hand hurts from writing notes.
To find the square root of a number, subtract every odd number from the number. You must always start with one guys!!!!!!
For example, 25-1=24, 24-3=21, 21-5=16, 16-7=9, and 9-9=0.
Now, it took us 5 odd numbers to get to zero, so the square root of 25 is 5.
If the odd number is bigger than the number you’re subtracting, you remember how many odd numbers it took for you to get here, and you go into the tenths, start from one again, and go. If your odd number is bigger than the number you’re subtracting, go to the hundredths… and so on. Afterwards, you add up all the values.
For example, 25-1=24, 24-3=21, 21-5=16, 16-7=9, and 9-9=0.
Now, it took us 5 odd numbers to get to zero, so the square root of 25 is 5.
If the odd number is bigger than the number you’re subtracting, you remember how many odd numbers it took for you to get here, and you go into the tenths, start from one again, and go. If your odd number is bigger than the number you’re subtracting, go to the hundredths… and so on. Afterwards, you add up all the values.
Mar 20, 2025
0
#13
I guess it's not a "trick" but it's kinda cool. If you take any number not divisible by 3 and write it 3 times (5=555) it will always be divisible by 3
Post math tricks here
for example, a% of b=b% of a, meaning 8% of 25 is 25% of 8, which is 2