past exams again help!!!!!!2008

[dreamz]

i need help on all of them!!!!!!!!plz with explanation

[sir0004]

For the first one, imagine a cylinder (the image is what you get when you cut the cylinder in half- roll a book and imagine it being cut and this is the shape that is given). First treat it as if it is NOT cut, and find the area of the two circles and the middle part (the equation is  3.14 * (.75)^2 * 2 + (2 * 3.14 * .75 * 2.5)). Now remember how the cylinder is cut in half...so divide this ans by 2. Then the question says INCLUDE base area (which is 1.5 * 2.5) and this is added to previous answer. Overall you get 11.4076

[sir0004]

For the second one, remember that any conical shape would mean the volume you get must be divided by 3 (this is a RULE). So do 1.3^2 * 3.14 * 1.2. Then divide this by 3 to get 2.12264

[sir0004]

For the last/third one, draw lines connecting the directly opposite edges such that you get 6 triangles. Then take one of the triangle and put a line through the middle, recognizing that the length of this line is 5.2/ 2 cm. Now you have a right angle triangle and use Pythagoras to find the base of this triangle (also recognizing that this is a regular hexagon and so all sides are 3cm). Then multiply this base by 2 to get the base of one of the 6 triangles. then use the .5 * 2.99 * 2.6 rule to get 3.89 which is the are of one of the triangles.
Now multiply this by 6 (since 6 sides are apparent) to get 23.3479