SI CONVERSIONS

INTRODUCTION Sometimes it is necessary to convert measurements into other units. This is done very easily in the SI system, not so easily in standard units. How many cups are in a pint? How many yards are in a mile? It gets very confusing quickly. Not so in the SI system.

INTRODUCTION Conversions in the SI only require that you know the prefixes and their values, and that you can count to move the decimal point in the right direction.

INTRODUCTION There is a very easy way to remember the correct order of the basic prefixes. You will use a mnemonic to help you remember them.

LADDER METHOD Metric prefix chart: each step is a difference of 10. “King Henry Died By Drinking Chocolate Milk” smallerlarger

ACCELERATED ONLY

INTRODUCTION For each step you take on the ladder to the left or the right you are changing units by a factor of ten. For example: When you have 100 centimeters and you want to change it into deciliters you move 1 step to the left.

INTRODUCTION Centimeters Decimeters

INTRODUCTION What you are doing is dividing by ten to convert centimeters into decimeters. 100 centimeters divided by 10 would be ten decimeters. 100 ÷ 10 = 10

INTRODUCTION To convert between metric units, start at the unit given on the Ladder Handout and move your decimal in the direction of the unit you want to convert to.

CONVERSION EXAMPLE Convert 100 cm to decimeters Deci is 1 place to the left of centi so move your decimal 1 place to the left: 100 cm can be written 100. cm By moving the decimal point 1 place to the left it becomes 10.0 decimeters

INTRODUCTION

SPECIAL NOTES If the decimal point is shown in the number you are converting that is your starting point for moving the decimal to the right or the left. If the decimal point is NOT shown in the number then it is always at the end of the number you are converting.

EXAMPLE Convert 1.25 meters to decimeters has a decimal point. Meters is a base, 1 place to the left of deci. Move the decimal point 1 place to the right meters is 12.5 decimeters.

INTRODUCTION From Here To Here

IN QUESTION Do you believe that time travel is possible? If so, would you be willing to volunteer to be the first person to try it?

VOCABULARY Record this definition in your notebook: Mnemonic – a memory tool to help you remember key facts.

NOTES To convert between numbers in the SI, use the Ladder Method to help you move the decimal in the correct direction. 1. Look for the decimal point as the starting place. 2. Find the starting step. 3. Find the finishing step.

NOTES 3. Count the number of steps you need to move the decimal. 4. Make sure you move the decimal in the correct direction. 5. Rewrite the conversion using the right units.

NOTES The order of prefixes is: King = kilo Henry = hecto Died – deka By = base units Drinking = deci Chocolate = centi Milk = milli

OUT QUESTION Convert these numbers: 1.Convert 20 deciliters to centiliters. 2.Convert 100 grams to kilograms. 20 deciliters = 200 centiliters 100 grams = 0.1 kilograms