# The Flying Colours Maths Blog: Latest posts

## An ex-straw-dinarily silly Fermi problem

Everybody sit down. Dominika has an important announcement. So…I have a confession to make. Despite the fact that I write maths comic strips, I’m actually a physicist. Pause for gasps of shock. Yes, terrible, I know. But physics in general has a little gem that I wish more people knew

## Ask Uncle Colin: How do I add things up?

Dear Uncle Colin, Is there an easy way to write series in sum notation? I have $1 + \frac{1}{2\sqrt{2}}+\frac{1}{3\sqrt{3}} + …$ but no real clue about how to put it into a compressed form. – Summing Is Giving Me Aneurysms Hi, SIGMA, and thanks for your message! I like to

## On a Crossnumber Clue

On a Crossnumber Clue In the Chalkdust Crossnumber #4, the deadline for which was last week, one of the first clues I looked at and thought “I can work that out easily enough” was this one: 27. The number of straight lines that go through at least two points of

## Ask Uncle Colin; A variable fraction

Dear Uncle Colin, I have a fraction, $\frac{x^2-x}{x-1}$, and I want to cancel it down to $x$ – but I'm not sure those are the same. Are they? – Got A Lot Of Interesting Sums Hi, GALOIS, and thanks for your message! The short answer is, yes and no. Everywhere

## A New Year’s Resolution For You (Only For Genius [sic])

Right, listen up, everyone. I know you've already made your new year's resolutions, and probably broken most of them by now, but I've got one for you to add to your list. It concerns images like this one: Anything with a picture of Einstein on it. Anything that says "only

## Ask Uncle Colin: Find me a circle!

Dear Uncle Colin, I have two points and I want to construct a circle of a given radius that passes through them. Is it possible? — Every Underspecified Circle Lives Its Dream Hi, EUCLID, and thanks for your message! There are three possible answers to this, depending on the size

## Some charitable suggestions

Some charitable suggestions Hello! I'm going to be a bit more personal than usual with this post; it's Boxing Day and in the spirit of goodwill to all, I wanted to highlight some of my favourite charities. As you know, the Flying Colours Maths blog is absolutely free of charge,

## Ask Uncle Colin: Why is it not 4?

Dear Uncle Colin, I have a binomial expansion of $(1+x)^\frac{1}{2}$ and need to approximate $\sqrt{5}$. Apparently you need to substitute in $x=\frac{1}{4}$, but I’d have thought $x=4$ was a more obvious choice. What gives? — Roots Are Dangerous If Understood Sloppily Hi RADIUS, and thanks for your message! That does

## Some exam technique tips for the new GCSE

Reports are filtering in to Flying Colours Towers about the mock exams recently taken by year 11s. Words like 'bloodbath' and 'disaster' feature prominently (my students, I should add, have acquitted themselves well and are in line to be mentioned in dispatches for bravery.) There's a reason the new-style papers

## Ask Uncle Colin: How do I multiply big numbers together?

Dear Uncle Colin, How do you multiply big numbers like $2158 \times 1812$? I try to do it using the column method or the grid, but I always make mistakes. — A Desperately Desired Error Reduction Hi, ADDER, and thanks for your message! I’ve been playing with something midway between