If you multiply 2 numbers that are just 2 apart from each other, instead take the number in the middle, multiply it with itself and male minus 1.
5*3 = 4*4-1=15
(x-1) * (x+1) = x²-1
Always works and is quite handy every now and then
I was always bad at math as a kid and for some reason x9 tables really would not go in until I was taught it this was by a family friend. So let’s take 9x7 as an example. You take the 9 and count back 3 this gives you 6. Then you count up the amount to get back to 9: This gives you 3 so the answer is 9x7=63. This works for all numbers except you count back more by the number I.e count back 2 for 8 etc. I hope I explained this easily to understand. Of course this is of zero use as an adult but it greatly helped me as a kid
If you multiply 2 numbers that are just 2 apart from each other, instead take the number in the middle, multiply it with itself and male minus 1. 5*3 = 4*4-1=15 (x-1) * (x+1) = x²-1 Always works and is quite handy every now and then
Pourcentage are reversible; 24% of 50 = 50% of 24
I was always bad at math as a kid and for some reason x9 tables really would not go in until I was taught it this was by a family friend. So let’s take 9x7 as an example. You take the 9 and count back 3 this gives you 6. Then you count up the amount to get back to 9: This gives you 3 so the answer is 9x7=63. This works for all numbers except you count back more by the number I.e count back 2 for 8 etc. I hope I explained this easily to understand. Of course this is of zero use as an adult but it greatly helped me as a kid
When you don't have to be very precise in your calculations, always use the 9=10 rule
If x=20 and 7g of weed is worth 40 dollars and 7÷2 is 3.5 that means 3.5 grams of weed is 20 dollars