Chp 9 Surface Area
Explain what surface area is (out loud)
The area of all the faces of a 3D shape
What is the formula for the area of a circle
A=pir^2
Formula for volume of a prism
V = Base area x height or l*w*h
Write the fraction as a percent: 1 3/8
1.375
Isaiah loaned out $1700 for 15 months at 16% annual simple interest. How much interest will he earn? And what will the balance be on the loan he made?
Interest = Prt. Interest = (1700)(0.16)(1.25) = $340
Balance = Principal + Interest
Balance = 1700 + 340 = $2040
Formula for surface area of a rectangular prism (box)
S = 2B + Ph or S= 2 base area + lateral area
Formula for the circumference of a circle
C=piD
Formula for volume of a cylinder
V=Base Area * height
V = pir^2h
75 visitors to a Sea World are surveyed. 30 say they like roller coasters. 45 say they prefer the animal shows. What percent like the roller coasters?
30/75 = 0.4 = 40%
What is the formula for percent of change?
change/original amount
Formula for surface area of a cylinder
S = 2B + lateral area or S = 2pir^2 + pidh
Find the area of a circle with a diameter of 10 meters in terms of pi.
A=pir^2=pi5^2=25pi m^2
Find the volume of the cylinder with these dimensions: radius of base is 8, height of cylinder is 2. Leave in terms of Pi.
V = Bh
V=pir^2h = pi8^2(2)=128 pi
Estimate 20% off a $14.99 nerf football is about how much off?
$14.99 is about $15. 20% = 1/5
1/5 of 15 = 3. $3
Normally the widget costs $27 but it is on sale for $20. What is the discount? (Or what is the percent of change?)
($27-20)/27 =25.9%
Find the surface area of a box with a length of 6, w = 4, h=10 cm
SA = 2Base Area + Lateral Area = 2B + (perimeter)(height)
SA = 48 + 200 = 248 units squared
If the circumference of a circle is 37.7 inches, what is the diameter? What is the radius?
C=piD
37.7=piD
37.7/pi = d = 12
Find the volume of a prism with triangular bases with b 4 and height of 3, and height of the prism is 10.
V=Base area * height
V= 1/2 (4*3) * 10
You buy lunch at a restaurant for $25.85. About how much money should you leave for a 15% tip?
15% = 10% + 5%. 10% of 26 is 2.60. Half of 2.60 is 1.30 which is 5%. $2.60 + 1.30 = $3.90 (you'll probably round up to $4.00)
Your favorite thing is usually $73. It is 30% off this week. What is the sales price?
How much is the discount: 0.30 (73) =$21.90
Sales price = Original - Discount
Sales price = $73 - 21.90 = $51.10
Find the surface area of a cylinder with a base radius of 4 and a height of 10 units
S = 2pir^2 + pidh
2pi4^2 + pi (8)(10) = 352 units^2
Complementary angles add up to
90 degrees (Memory trick: it's always RIGHT to give a compliment. Or corners and compliments are right)
They are congruent (angle measure is the same) When two lines intersect, the pairs of opposite angles are vertical angles.
31% of 180
.31(180) = 60
Clear fractions using LCM then solve.
1/5 x + 6 = 3/4
x = -26 1/4
LCM is 20, so multiply both sides by 20 to clear fractions then solve for x