r/CasualMath

If you take any number (that is not itself divisible by 17), and then square it, square its product, etc, you will always get a number that is one more than a number that is divisible by 17.

In six or less steps, I believe, which still leads to very high numbers.

I don't know what (((((89^2)^2)^2)^2)^2)^2)-1 is, but I do know it is divisible by 17. (Also, more easily, by 2, 3 and 5)

So my friend is turning 20, and he loves math and is really smart, i want to write a crazy looking equation on his present that equals 20. Any tips how to make one? Or does someone know of one?

Any number divided by 7 follows a recurring pattern after decimal. For example,

1/7 = 0.142857 (whole set recurring)

2/7 = 0.285714 (whole set recurring)

3/7 = 0.428571 (whole set recurring)

4/7 = 0.571428 (whole set recurring)

5/7 = 0.714285 (whole set recurring)

6/7 = 0.857142 (whole set recurring)

Also notice that the first digit after decimal increments to the next larger digit with every numerator increase.

Note: by recurring I mean this --

⅐ = 0.142857142857142857142857142857...

I learned this when I was young from my dad, decades ago. He passed away a few years ago. He was a professor.

I really need some help with this kind of maths problem.

Im doing a timed assessment for a role I’m applying for. I cant use a calculator. I dont find the maths particularly hard. I can work it out when i have the time. The problem is i cant seem to do it at the speed i need to and i keep getting below average on practice questions because im taking so long.

Are there any tips or advice for ways to quickly work out this kind of question. Assuming i have 12 minutes to answer 20 questions.

Mrs Fuller wants to return a t-shirt, a pair of designer shoes, a dress and a pair of jeans, which cost £12.95, £85.99, £17.99 and £22.99 respectively. How much does she stand to gain if all the items are returned?

£149.92
£133.92
£132.92
£139.91
£139.92