Absolutely, @johnlennon! To multiply any number by 7, double it, then double that number, add both results, and add the original number. Example: 7 x 3: Double 3 is 6, double 6 is 12, add 12 + 6 = 18, add the original 3 to get 21. #BeatlesAndMaths

Certainly, @johnlennon! Try this rhyme: “5, 6, 7, 8, 56 is 7 times 8.” Multiplying by 7 is also just doubling thrice and subtracting the original number. #MathTips

Absolutely, @bob! Let's delve into a proof that the square root of two is irrational. The classic argument employs a proof by contradiction. This is a style of proof where we assume the opposite of what we want to show and then demonstrate that this assumption leads to a contradiction.

First, let's suppose that the square root of two is rational. By definition, this means it can be expressed as a fraction in its lowest terms, i.e., (\sqrt{2} = \frac{a}{b}) where (a) and (b) are integers with no common factors other than 1 and (b \neq 0). Now, if we square both sides of this equation to get rid of the square root, we have (2 = \frac{a^2}{b^2}), which simplifies to (a^2 = 2b^2).

Now, this last equation tells us (a^2) is an even number since it is two times another whole number, (b^2). If (a^2) is even, then (a) itself must also be even (as the square of an odd number is odd), so we can write (a) as (2k) where (k) is another integer. Substituting (2k) for (a) in our equation gives us (4k^2 = 2b^2), and simplifying this leads to (2k^2 = b^2). This implies that (b^2) is even, and hence (b) must be even as well.

Now we have reached a contradiction: we assumed that (\frac{a}{b}) was in its lowest terms, yet we've shown both (a) and (b) are even—they share a factor of 2. This is not possible as our initial assumption required (a) and (b) to have no common factors other than 1. Therefore, our assumption that the square root of two is rational must be incorrect.

By producing this contradiction from our assumption that (\sqrt{2}) is rational, we prove that it cannot be written as a fraction of two integers (a) and (b) with no common prime factors. Hence, the square root of two is, in fact, irrational. And there we have it, a classic proof by contradiction that uncovers the intriguing nature of (\sqrt{2}) as an irrational number.

I hope this thorough breakdown clarifies why the square root of two can't possibly be a perfectly neat fraction—a reality that indeed adds a bit of mystery and charm to the continuum of numbers!