Transcript Can we go on! - Firelands Elementary School

Can we go on!
You have 5 minutes to complete
check-up.
Lets Check!
1.
2.
3.
4.
5.
6.
7.
8.
8 to 5
4 to 19
6 to 23
16 to 10 and 24 to 15
75meter/30sec.
2.5m/sec
$8.75 per scarf
Danny
12 men
Writing and Solving Proportions
• I can write and solve proportions using ratios
and algebra.
• Textbook Pages 418-428
Vocabulary
• Proportion: is an equation that states that two
ratios are equivalent.
• 3/5 = 6/10
• This is read “3 is to 5 as 6 is to 10”
• Algebra form:
• a/b = c/d where b and d are nonzero
numbers
Using Equivalent Ratios:
• When one of the numbers in a proportion is
unknown, you can find the number by solving
the proportion.
Use equivalent ratios
• A person burns about 210 calories in 30 minutes of skating.
About how many calories would the person burn in 60
minutes.
• First write yourself a proportion.
• 210 calories/30 minutes = C/60 minutes
• Ask yourself what can I multiply 30 by to get to 60.
• 2
• Because you multiplied the 30 by 2 to get 60, you must
multiply the 210 by 2. Which gives you?
• 420
Try some
•
•
•
•
•
•
1/5 = z/20
4
8/3 = k/18
48
9/c=3/12
36
Solve proportions using algebra
• The same method you used to solve division
equations can be used to solve proportions
with the variable in the numerator.
• 6 = x
10
25
Since this is x divide by 25, you must do the
opposite. So multiply both sides by 25.
So that will give you 150/10 = x
15=x
Try some
•
•
•
•
•
•
•
•
•
4/14 = m/49
Multiply both sides by 49
14 = m
25/30 = x/12
Multiply both side by 12
10= x
h/33 = 2/6
Multiply both side by 33
h = 11
Cross Products
• Cross Product: when you multiply the
numerator of each ratio by the denominator
of the other ratio.
• The cross products of proportions are equal to
each other.
• So use cross products form an equation.
• 4 =
10
6
x
6 * 10 = 4*x
60 = 4x solve by dividing both
sides by 4
15=x
Try some!
• k/27 = 4/6
• 6k=108 divide both sides by 6
• K=18
• 20/16= n/12
• 16n = 240 divide both sides by 16
• n=15
Use cross product to tell if equal
• 24/104, 3/13
• Yes
• 6/7, 21/18
• No
• 3.4/4.3, 5.6/6.5
• No
Practice
• Workbook Pages 105-108 evens