## Thursday, March 18, 2010

Rectangular Prisms

To find the surface area of a rectangular prism you have to find the area of the side, the top, and the front. multiply each of those areas by 2 and add together.
top:
lxw
12x4.5
54x2
=108

side:
lxw
10.4x4.5
46.8x2
=93.6

front
lxw
12x10.4
124.8x2
=249.6
Area:108+93.6+249.6= 451.2 cm 2

Triangular prism

To get the area of a triangular prism multiply base by height and divide by 2.That is the triangle. Now for the rectangles multiply length by width for each one, and add each of the measurement together.
(b × h) ÷ 2 = A
L × W = A
L × W = A
(2 × 2) ÷ 2 = A
5 × 3 = A
5 × 2 = A
2cm* = A
15cm* = A
10cm* = A
2cm+2cm+15cm+15cm+10cm
= 44cm

Cylinder prism

First multiply Pi by radius by radius to get the area of the circle. Then to get the area of the rectangle multiply pi by base by height. Add the answers together and you have the answer.

R= d/2
R= 5/2
R= 2.5cm
C= (pi)d
C= 3.14(5)
C= 15.7cm
(10cm)
A= lxw
A= 15x15.7
A= 235.5cm(2)
A=(pi)rr
A= 3.14x 2.5 x 2.5
A= 19.625cm(2)
Area: 19.625+19.625+235.5
Area: 274.57

R=d/2
C=(pi)d
A= lxw
A= (pi)rr

So we did a test and, Harbeck told us to take a few questions out of it and put it on the growing post.No problem.Here are 5 questions I chose.
1.3/4 x 7/8.
Times the numerator by the numerator. 3 x 7= 21.
denominator x denominator (4 x 8) = 32. 21/32.
The next question I did was q.5
5.
4 7/8 x 1/7. Pretty much the same but we have to change the mixed fraction to a improper fraction.4 groups of 8 = 32. 32 + 7 = 39. 39/8.39 x 1= 39, 8x 7=56. 39/56.
The next question I did was q.7
7.
13/7 x 32/5 .Now we just have to change both numbers.1 group of 7=7. + 3 = 10.10/7.3 groups of 5 =15.+2= 17.10x17=170.7x5 =35. 170/35. Simplify. 170/35 divided by 5 = 34/7. Now we have to mix the fraction. 66/7
Then Harbeck told us to do these questions
11/2 divided by 3/4. How many times does 3/4 go into 11/2. Twice.You have to make the numbers into the most common denominator.11/2 into 12/4.3/4 goes into 11/2 Twice.
3/4 divided by 1/2. How many times does 1/2 go into 3/4. 1/2 also = 2/4.So it goes into it two thirds of the way. 1/2 goes into 3/4, 2/3 times.

#### 1 comment:

1. to any body who reads this blog, i have no idea why it went and got blown up at the end.