Transcript Week #23 Bell Ringers & Quiz - Mrs-Cook-8th-Grade-Math

Week #23 Bell Ringers & Quiz
8th grade math
Bell Ringer
Monday
Figure A is dilated to create Figure B.
A
B
2 in
4 in
1.
2.
3.
4.
5.
1 in
3 in
1.5 in
6 in
What type of dilation occurred?
Calculate the scale factor.
Calculate the original volume.
Calculate the new volume.
How is the volume affected?
Figure A is dilated to create Figure B.
A
B
3 in
2 in
4 in
1 in
1.5 in
6 in
1. What type of dilation occurred?
Enlargement
2. Calculate the scale factor.
New
6 3
   1.5
Original 4 2
Figure A is dilated to create Figure B.
A
B
3 in
2 in
4 in
1 in
1.5 in
6 in
3. Calculate the original volume.
lwh  4(1)( 2)  4(2)  8in
3
4. Calculate the new volume.
lwh  6(1.5)(3)  9(3)  27in
3
Figure A is dilated to create Figure B.
A
B
2 in
4 in
1 in
3 in
1.5 in
6 in
5. How is the volume affected?
Say NO to Oreos!
New
27
3

 3  3.375
Original
8
8
The new volume is 3 3/8 times
larger than the original volume.
Quiz
Monday
Calculate the scale factor used to dilate
the triangle.
Calculate the scale factor used to dilate the triangle.
What is the scale
factor?
New
Original
21 3

14 2
3
ScaleFactor  or1.5
2
Triangle ABC
Enlargement
AB= 14 cm
BC= 12 cm
A’C’= 21 cm
B’C’= 18 cm
To find the scale factor, I divided the new
dimension by the original dimension. Since, the
new dimensions are larger, an enlargement
occurred. Since it is an enlargement, the scale
factor should be greater than 1.
The scale factor is 1.5.
Bell Ringer
Tuesday
2 ft
4
ft
9 ft
1. Calculate the amount of fencing needed
for the rectangular pen.
2. Calculate the amount of fencing needed
for the circular water trough.
3. Calculate the square footage of grass.
2 ft
9
ft
4
ft
1. Calculate the amount of fencing
needed for the rectangular pen.
P=4+9+4+9
P = 13 + 13
P = 26 ft
2 ft
4
ft
9
2. Calculateft
the amount of fencing
needed for the circular water trough.
C = 2πr
C = 2 (3.14) (2)
C = (6.28) (2)
C = 12.56 ft
2 ft
4
ft
9
3. Calculate theftsquare footage of grass.
. A rect. = lw
A = 4(9)
A = 36 ft2
A circle = πr2
A = (3.14) (22)
A = 12.56 ft2
Area
Shaded:
36 – 12.56
23.44 ft2
Quiz
Tuesday
At an auto parts factory, Audrey can
press an average of 16 gears in 30
minutes. At this rate, how many
hours will it take for her to press
400 gears?
At an auto parts factory, Audrey can press an average of 16 gears in 30 minutes.
At this rate, how many hours will it take for her to press 400 gears?
How long will it
take?
16 gears 400 gears

30 min
x min
16 gears in 30 minutes
400 gears
hours
To find the number of minutes it will take
to press 400 gears, I set up a proportion. I
multiplied by a scale factor of 25. I divided
the number of minutes by 60 to convert to
hours.
16 gears  25 400 gears

30 min  25
750 min It will take 12.5 hours to
750 min
press 400 gears.
 12.5hrs
60 min
Bell Ringer
Wednesday
Jackie built a fence around her garden to keep
animals out. The dimensions of the area enclosed by
the fence are shown in the diagram.
1. How many feet of fencing was needed?
2. Calculate the number of square feet enclosed by
the fence.
Jackie built a fence around her garden to keep
animals out. The dimensions of the area enclosed by
the fence are shown in the diagram.
1. How many feet of fencing was needed?
6ft
6ft 8.5f
t
15 - 9=6ft
18 - 12=6ft
P  AddAllSides
6 6 c
2
36  362  c
72  c
2
72  c
8.5  c
2
2
2
P  8.5  9 12 15 18
P  62.5 ft
Jackie built a fence around her garden to keep animals out.
The dimensions of the area enclosed by the fence are shown in
the diagram.
2. Calculate the number of square feet enclosed by the fence.
6ft
2
18
ft
6ft
180
ft2
A  180  18
2
A  198 ft
Arect  lw
A  (12)(15)
2
A  180 ft
bh
6(6)
Atri 
A
2
2
36
2
A
 18 ft
2
Quiz
Wednesday
The isosceles trapezoids are similar. What is the
length in centimeters of each base of the isosceles
trapezoid PQRS?
A.
b1 = 7
b2 = 10
B.
b1 = 4
b2 = 10
C.
b1 = 6
b2 = 8
D.
b1 = 9
b2 = 18
The isosceles trapezoids are similar. What is the length in centimeters of each
base of isosceles trapezoid PQRS?
What is the length
of each base?
New
4 2
 
Original 6 3
b1 9 6


b2 12 8
2
9
3
2
12 
3
C:
b1  6 & b 2  8
Similar trapezoids
KL = 9 cm
NM = 12 cm
LM = 6 cm
PS = 4 cm
I found the scale factor used by dividing the
new side by the original side. I multiplied
both bases by the scale factor to get the new
dimensions of trapezoid PQRS.
The length of the bases are 6
cm and 8 cm.
Bell Ringer
Thursday
1. During a sale Sasha paid $25.00 for a pair
of shoes that had a regular price of
$35.00. What was the percent discount on
the pair of shoes?
2. A sequence of numbers was generated
using the rule 3n − 2, where n represents a
number’s position in the sequence. Write the
first four terms of the sequence.
1. During a sale Sasha paid $25.00 for a pair of
shoes that had a regular price of $35.00. What
was the percent discount on the pair of shoes?
35  25  $10
10 2
  .28  28%
35 7
Range : (28%  29%)
2. A sequence of numbers was generated using
the rule 3n − 2, where n represents a number’s
position in the sequence. Write the first four
terms of the sequence.
1
1
3(1)  2
3 2 1
2
4
3(2)  2
62  4
3
7
4
10
3(3)  2
92  7
nth
3n-2
3(4)  2
12  2  10
Quiz
Thursday
Nadia bought 7 lawn chairs that cost $9.49
each. The tax rate was 8.25%. Which
equation can be used to find c, the total
cost of the chairs, including tax?
A c = 7(9.49)(0.0825) + 0.0825
B c = 7(9.49) + 0.0825
C c = 7(9.49)(0.0825)
D c = 7(9.49) + 7(9.49)(0.0825)
Nadia bought 7 lawn chairs that cost $9.49 each. The tax rate was 8.25%. Which
equation can be used to find c, the total cost of the chairs, including tax?
Which equation can
be used?
7 chairs
$9.49 each
8.25% tax
ChairCost :
# chairs(cha ir cost)
Tax :
TotalCost : ChairCost (TaxRate)
I wrote down what I would do to solve the
problem. I need to find the total cost of the
chairs by multiplying the number of chairs by
the chair cost. To find the tax, I multiply the
chair cost by the tax rate (converted to a
decimal). I add the tax to the chair cost for
the total cost.
ChairCost  Tax
Equation D can be used.
D:
7(9.49)  7(9.49)(0.0825)
Bell Ringer
Friday
1. How many square feet of material
is needed to make the tent?
2. How much ground space do we need
to put up the tent?
8.1 ft
7 ft
8.1 ft
12 ft
16 ft
1. How many square feet of material
is needed to make the tent?
Front : 8.1(12)  97.2 ft
2
Back : 8.1(12)  97.2 ft
2
Bottom : 16(12)  192 ft
16(7) 112
2
Side :

 56 ft
2
2
2
TotalS  97.2  97.2  192  56  56  498.4 ft
2
8.1 ft
7 ft
8.1 ft
12 ft
16 ft
2. How much ground space do we need
to put up the tent?
Bottom : 16(12)  192 ft
8.1 ft
7 ft
8.1 ft
12 ft
16 ft
2
Quiz
Friday
Canoe rentals are as follows:
6 hours: $30.00
1 hour: $7.00
You are planning a 5 hour canoe trip.
Which rental will give you the best rate?
Canoe rentals are as follows:6 hours: $30.00; 1 hour: $7.00
You are planning a 5 hour canoe trip. Which rental will give you the best rate?
Which rental is
cheaper?
$30
x

6hrs 1hr
$7
1hr
1
$30 
6  $5
1 1hr
6hrs 
6
$7  5  $2cheaper
6 hours = $30
1 hour = $7
5 hour rental
To find the unit rate, I divided the rental price
by the number of hours. I multiplied by a
scale factor of 1/6. For $30, it is $5 per hour.
This is $2 cheaper than renting it for $7 per
hour.
The $30 for 6 hours rental is the
cheapest.