E Maths - Volume

• bonkysleuth

  7 Aug 09, 01:54

  ABCD represents the rectangular sloping surface of a solid. ABEF is a rectangle which is horizontal and CE and DF are vertical lines. AB = DC = FE = 40 cm, BC = AD = 30 cm , angle CBE = angle DAF = 35 deg

  

  Jumped to the last question.

  Find the volume of the solid ABEC when it is cut off from the solid.

  The previous questions were find AC, CE and angle FAE (for guiding purposes)

  I got 4226cm3 if I remember correctly. I make use of the fact that a rectangle could be form using an exact replica of the shape. Next I find the volume of rectangle which is AB X BE X EC and to get volume of the solid ABEC, I merely multiply 0.25 to volume of rectangle. However the anwer is 2820cm3

• yiha093

  7 Aug 09, 12:36

  the 2 figures are similar

  if abec removed from solid

  so i guess i wil use the

  (L1/ L2 )^3= V1/V2

• yiha093

  7 Aug 09, 17:24

  can sum1 help too ?  my maths not very good.

• Mikethm

  7 Aug 09, 19:12

  cos 35 = BE/30

  BE  = 30 cos 35

  sin 35 = CE/30

  CE = 30 sin 35

  Volume of ABEC

  = 1/3 x base area x height

  = 1/3 x (1/2 x AB x BE) x CE

  = 1/3 x (1/2 x 40 x 30cos 35) x 30sin 35 

  =2819.07

  =2820cm^3 (3sf)

  Lesson here... KEEP IT SIMPLE. Don't try stunts.