Please use the menu on the left to navigate through this resource
Walking Backwards Programme Outline
To pass the Guard, Lisa must 'have less than nothing in this world'. In trying to work that one out, she discovers negative numbers. The Wizard finally provides the solution, however, by making Lisa borrow money from the Guard for a bowl of porridge. Thus in debt, she's free to go on her way. Start to 03:40 - A puzzle Lisa is barred from crossing the bridge until she learns to 'have less than nothing in this world'. Exploring a number line marked on the bridge, she discovers negative numbers - but the guard, unimpressed, observes that numbers are abstract things. He wants a concrete answer to the puzzle. |  | 03:40 to 04:27 - The Mathematical Encyclopaedia The Encyclopaedia opens to page 'negative one', and proceeds to tell us of the history of negative numbers. They were, it says, invented by accountants, not pure mathematicians. |  | 04:27 to 08:55 - Arithmetic The Wizard arrives on the bridge, and (obliquely, as ever) suggests that Lisa and the Guard try some arithmetic. It will, he says, 'open the pathways to a higher understanding', and help them solve the puzzle. Unconvinced, Lisa continues to tramp up and down the number line, as the Guard writes down calculations for her to do. |  | 08:55 to 10:00 - Multiplication rules With the aid of a few bits of twig, the Wizard describes the rules one must follow when multiplying negative and positive numbers together. He ends up with a table showing which combinations give positive and which give negative results. As we leave him, he's trying to remember where he left his porridge. |  | 10:00 to End - Porridge Lisa and the Guard have sullenly given up tramping up and down the number line, feeling no closer to a solution. The Wizard arrives, with a pot full of his delicious porridge, which he offers for a bargain price. To buy a bowl, Lisa borrows money from the Guard, which she realises allows her across the bridge. At first indignant, the Guard finally realises that owing money is just like having negative money - having less than nothing in the world. |  |
|
