Sexagesimal system

     Sexagesimal is a numeral system in which each unit is divided into 

60 units of lower order, that is to say, it is a base-60 number system

The sexagesimal system was used by the Sumerians and Babylonians.

 It is currently used to measure time and angles

1 h 60 min 60 s

1º 60' 60''

Converting Sexagesimal into Decimal Form

Convert 3 hours, 36 minutes, 42 seconds to seconds.

Converting Decimal into Sexagesimal Form

1To convert to major units, divide.

7,520''

2To convert to minor units, multiply.

For the measurement of time and angles, the following steps can be performed:

Addition

1. Place the hours under the hours (or the degrees under the degrees), the minutes under the minutes and the seconds under the seconds and add together.

2. If the seconds total more than 60, they are divided by 60, the remainder will remain in the seconds column and the quotient is added to the minutes column.

3. Repeat the same process for the minutes.

Subtraction

1. Place the hours under the hours (or the degrees under the degrees), the minutes under the minutes and seconds under seconds and subtract.

2. If it is not possible to subtract the seconds, convert a minute of the minuend into 60 seconds and add it to the minuend seconds. Then, the subtraction of the seconds will be possible.

3. Repeat the same process for the minutes.

Multiplication by a Number

1. Multiply the seconds, minutes and hours (or degrees) by number.

2. If the seconds exceed 60, divide that number by 60, the remainder will remain in the the seconds column and the quotient is added to the minutes column.

3. Repeat the same process for the minutes.

Division by a number 

1. Divide the hours (or degrees) by the number.

Divide 37º 48' 25'' by 5.

2. The quotient becomes the degrees and the remainder becomes the minutes when multiplied by 60.

3. Add these minutes to the minutes column and repeat the same process for the minutes.

4. Add these seconds to the seconds column and then divide the seconds by the number.

Worksheet

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Equations

What is an Equation

An equation says that two things are equal. It will have an equals sign "=" like this:

x

+

2

=

6

That equation says: what is on the left (x + 2) is equal to what is on the right (6)

So an equation is like a statement "this equals that"

Parts of an Equation

So people can talk about equations, there are names for different parts (better than saying "that thingy there"!)

Here we have an equation that says 4x − 7 equals 5, and all its parts:

A Variable is a symbol for a number we don't know yet. It is usually a letter like x or y.

A number on its own is called a Constant.

A Coefficient is a number used to multiply a variable (4x means 4 times x, so 4 is a coefficient)

Sometimes a letter stands in for the number:

Example: ax² + bx + c

• x is a variable
• a and b are coefficients
• c is a constant

An Operator is a symbol (such as +, ×, etc) that shows an operation (ie we want to do something with the values).

A Term is either a single number or a variable, or numbers and variables multiplied together.

An Expression is a group of terms (the terms are separated by + or − signs)

So, now we can say things like "that expression has only two terms", or "the second term is a constant", or even "are you sure the coefficient is really 4?"

Writing Algebraic Equations

Problem:	Jeanne has $17 in her piggy bank. How much money does she need to buy a game that costs $68?
Solution:	Let x represent the amount of money Jeanne needs. Then the following equation can represent this problem:
	17 + x = 68
	We can subtract 17 from both sides of the equation to find the value of x.
	68 - 17 = x
Answer:	x = 51, so Jeanne needs $51 to buy the game.

In the problem above, x is a variable. The symbols 17 + x = 68 form an algebraic equation. Let's look at some examples of writing algebraic equations.

Example 1:	Write each sentence as an algebraic equation.
	Sentence Algebraic Equation A number increased by nine is fifteen. y + 9 = 15 Twice a number is eighteen. 2n = 18 Four less than a number is twenty. x - 4 = 20 A number divided by six is eight.

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Example 2:	Write each sentence as an algebraic equation.
	Sentence Algebraic Equation Twice a number, decreased by twenty-nine, is seven. 2t - 29 = 7 Thirty-two is twice a number increased by eight. 32 = 2a + 8 The quotient of fifty and five more than a number is ten. Twelve is sixteen less than four times a number. 12 = 4x - 16

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Example 3:	Write each sentence as an algebraic equation.
	Sentence Algebraic Equation Eleni is x years old. In thirteen years she will be twenty-four years old. x + 13 = 24 Each piece of candy costs 25 cents. The price of h pieces of candy is $2.00. 25h = 200 or .25h = 2.00 Suzanne made a withdrawal of d dollars from her savings account. Her old balance was $350, and her new balance is $280. 350 - d = 280 A large pizza pie with 15 slices is shared among p students so that each student's share is 3 slices.

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Summary:

An algebraic equation is an equation that includes one or more variables. In this lesson, we learned how to write a sentence as an algebraic equation. Resolviendo ecuaciones, para practica

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