Sunday, October 10, 2010

Jemineth's Blogpost

Hi guys! My apologies because this blog was supposed to be up here ages ago. Anyways, i was assigned to work on the question No.15(b) from the textbook so here it is. P.S There WILL BE MISTAKES so feel free to comment and make corrections.

No.15 (b)
Twila made the object shown.

Length = 12 cm
Width = 3 cm
Height = 8 cm (For those who are having troubles seeing the measurements)

#1 : Find the area of each face(Because i know that the front/ back, sides, and top/bottom are asymmetrical, what I'm going to do is solve for one face and multiply it by two, to find the other.

Top and bottom :
3 x 12 x 2 = 72 cm2
Sides :
8 x 3 x 2 = 48 cm2
Front and back :
8 x 12 x 2 = 192 cm2

#2 : Once the area of all faces has been solved, you add them all together to find the surface area of the whole figure (without the hole in the middle)

72cm2 +48cm2 +192cm2 =312cm2

#3 : Find the area of the hole in the middle of the figure. To do that use the formula of a cylinder.

2 x π x r2 + 2 x π x r x h =
First solve the first part of the formula -
2 x π x 22 = 25.12
Next solve the second part of the formula -
2 x π x 2 x 3 = 37.68
Then add those two, to solve for the final answer of the formula
37.68 + 25.12 =62.80

#4 : Add the area of the hole to the area of all the faces to find the total surface area of the whole figure including hole in the middle.

62.80+312 = 374.8cm2

#5 : Last but not the least subtract the two ends of the hole from the surface area to get the final answer.

374.8- 25.12= 349.68cm2

There is my scribe post for number 15. Remember that there were mistakes from the way i solved for the answer, so please make corrections so that when other people reads this they will get the right answer, it also helps me too! Anyways, i hope my scribe wasn't hard to understand. And DO YOUR HOMEWORK GUYS !


  1. Its "the front/ back, sides, and top/bottom are SYMMETRICAL."

    And I think it should be (surface area of rectangular prism) + (2πrh) - (2πrsquared).

  2. Oh yeah , typo. . sorry. And thanks :)

  3. And you don't add 62.80(SA of cylinder) to 312(SA of rectangular prism). You add the 37.70(Area of the rectangle for the cylinder) to the 312, then subtract the 2 circles.