[OK] Privacy Policy  -  Terms & Conditions  -  See DetailsWe use cookies to personalise content and ads. We also share information about your use of our site with our advertising partners who may combine it with other information you've provided to them or they've collected from your use of their services.

Puzzle Details

My brother, Neville, struggles with mathematics a little.

I recently asked him to buy me some ribbon for my daughter's pretty pink bonnet.

He went to the haberdashery shop for the required length but accidentally interchanged the feet and inches.

When I measured the resulting ribbon I only had 30% of the length I required.

How much ribbon did I originally ask for?

I asked for 9 foot 2 inches (110 inches) and my brother brought me 2 foot 9 inches (33 inches).

I asked him to buy me A feet and B inches, which is a total of 12A + B inches. Neville accidentally bought me B feet and A inches, which is 12B + A.

We know that 12B + A is actually only 30% of what we wanted, so:

12B + A = 0.3 x (12A + B)

Multiply throughout by 10:

120B + 10A = 3 x (12A + B)

120B + 10A = 36A + 3B

117B = 26A

The first number where this gives a sensible answer is when A = 9, and B = 2. QED.

Our Favourite Illusions

 Shadow Illusion Are the squares A and B the same colour? Spinning Dancer Which way is the dancer spinning? Impossible Waterfall? Is the water flowing uphill in this impossible waterfall? The Butterfly A colourful butterfly?
 Duck Or Rabbit? Is this a duck or a rabbit? Hidden Faces Can you find his three daughters as well? Blind Spot An amazing demonstration of your blind spot. Impossible Prongs? Impossible prongs?
 What Am I? Can you tell what this is a picture of? Who Turned To? Who is missing? Same Eyes? Are her eyes the same colour? Parallel Cafe Wall Lines? Are the horizontal lines parallel?