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Friday, October 16, 2009

Eleven Plus and the Wear Out

A remark that sometimes made in eleven plus circles:

“This is wearing out my brain.”

For most of us the items that appear to wear out with terrifying rapidity are our tyres. Years ago motorists were told to rotate their tyres to increase wear – but today we are warned that this can be counter productive.

Discuss tyre pressures with your eleven plus child – after all `you never know . . . . . It might come up . . . . . .” Talk about keeping the tyres balanced – as this is supposed to maintain the health of the tyre. Then think of some tyre related questions.

Grand dad is still a little old fashioned. He bought a new car two years ago and it is his pride and joy. He keeps his spare tyre in his car. He did not want one of those funny little skinny tyres. He wanted the real thing – a tyre he could use if he got a puncture. (The garage had to take the thin reddish looking tyre out of the car and order a special wheel and tyre for grand dad.)

Over the last two years he has driven 10 000 miles. He rotated the tyres at intervals, so that by the end of the period each tyre had been used for the same number of miles. For how many miles was each tyre used?

Grandmother thinks that he has gone a little loose in the head – but she puts up with his idiosyncrasies. Sometimes she is not sure why. She is, however, an ex head teacher so knows a thing or two about education and the eleven plus.

“How many miles did the car travel?”

“Ten thousand. It said so.”

“How many tyres were there?”


“If each tyre had been used for four fifths of the journey, how many miles did each tyre travel?”

“Eight thousand miles.”

“How did you do that?”

“Easy. One fifth of ten thousand is two thousand. so four fifths is two thousand times four.”

“Why did we use four fifths?”

“There were five tyres – but there can be only four in use at one time. The other tyre is a spare so it stays in the boot.”

Of course every parent will now be on full alert. A spare tyre? Dear, oh dear! Back to the gym. Back to swimming. Sack the tutor. Engage that rather dishy personal trainer at the club. The spare tyre around your waist is one tyre that you do want to wear out.

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