Calculate the following: (−10) × (5 − 2) and (−10) × (2 − 5).
(−10) × (5 − 2) = (−10) × 3 = −30
(−10) × (2 − 5) = (−10) × (−3) = 30
The first calculation is a negative number multiplied by a positive number and is negative, the second calculation is a negative number multiplied by a negative number and is positive.
A lottery scratch game would be won if the card revealed a temperature lower than −8 degrees centrigrade. A gambler bought a card which revealed −6 degrees. She thought she had won, the shopkeeper thought she had won, but Camelot thought she had lost. Who was right?
Camelot were right. Minus eight is a smaller number than minus six. If we take away eight, we lose more than if we take away six. The number line shows this:
smaller ← . . . −10 −9 −8 −7 −6 −5 −4 −3 −2 −1 0 1 2 3 4 5 6 7 8 9 10 . . . → bigger
She said "I phoned Camelot and they fobbed me off with some story that −6 is higher — not lower — than −8 but I'm not having it."
This story made the national news, e.g. Private Eye number 1198, 23 November 2007.
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Last updated: 2 December, 2008.