Mental MathMental Math

You’ve been trapped alone in the jungle. A helicopter can pick you up in 45 minutes. You don’t have a watch and can’t arrive early or late otherwise jungle lions will eat you. There is hope!!! Each of your shoe laces burn for exactly one hour if you light one at one end. The laces burn at variable rates throughout the lace. How can you time 45 minutes and escape to freedom?

You’ve been trapped alone in the jungle. A helicopter can pick you up in 45 minutes. You don’t have a watch and can’t arrive early or late otherwise jungle lions will eat you. There is hope!!! Each of your shoe laces burn for exactly one hour if you light one at one end. The laces burn at variable rates throughout the lace. How can you time 45 minutes and escape to freedom?

MeasurementMeasurement

“The memory of misery approaches zero as the memory of joy approaches infinity”

“The memory of misery approaches zero as the memory of joy approaches infinity”

IntroductionIntroduction

History The Egyptians and the royal

cubit The pyramids

History The Egyptians and the royal

cubit The pyramids

The Greeks and the fathomThe Greeks and the fathom

War ship lengths

What is the problem with these measurements?

War ship lengths

What is the problem with these measurements?

Metric UnitsMetric Units

Common Units of Measurement Millimetres (10 per centimetre) Centimetres (100 per metre) Metres (1000 per Kilometre) Kilometre (Notice a pattern?)

Common Units of Measurement Millimetres (10 per centimetre) Centimetres (100 per metre) Metres (1000 per Kilometre) Kilometre (Notice a pattern?)

Conversion Factor Conversion Factor

The conversion factor of metric distances occur in multiples of ten.

However there is also the: Terametre Gigametre Megametre Hectometre (hm) Decametre (dam) Decimetre (dm)

The conversion factor of metric distances occur in multiples of ten.

However there is also the: Terametre Gigametre Megametre Hectometre (hm) Decametre (dam) Decimetre (dm)

The StairsThe Stairs

There is a way to organize this mess. If we are converting from a larger unit to a

smaller unit (ex. cm => mm) we multiply See Handout

There is a way to organize this mess. If we are converting from a larger unit to a

smaller unit (ex. cm => mm) we multiply See Handout

ExampleExample

Ex.To convert 15 metres (m) to centimetres (cm) we multiply by 100 because it is two steps down the stairs. 15m x 100 = 1500cm

Ex.To convert 15 metres (m) to centimetres (cm) we multiply by 100 because it is two steps down the stairs. 15m x 100 = 1500cm

Example #2Example #2

If we are converting from a smaller unit to a larger unit (ex. M=>km) we divide (because there has to be less)

To convert 14 metres to kilometres (km)

If we are converting from a smaller unit to a larger unit (ex. M=>km) we divide (because there has to be less)

To convert 14 metres to kilometres (km)