03 Dec, 10:28AM in sunny Singapore!
Home → Homework Forum →

A primary 6 maths problem help.

Subscribe to A primary 6 maths problem help. 9 posts

Please Login or Signup to reply.
  • Chunghong2004
    Chunghong2004's Avatar
    60 posts since Feb '08
    • 09 Aug `08, 11:42AM

      Can some help me with this?

       

      Given the perimeter of a semicricle is 61.68, find the diameter of the circle taking that pie=3.14

       

      thanks.

  • Uncertain
    Uncertain's Avatar
    1,033 posts since Jan '07
    • 09 Aug `08, 11:48AM

      (0.5)(3.14)d + d = 61.68

      LHS: test student alegbra <-- they should know what to do

      Then divide to find "d". This is still within primary school student capability

  • MyPillowTalks
    MyPillowTalks's Avatar
    15,791 posts since Nov '06
    • 09 Aug `08, 12:13PM

      Circumference of semicircle = 1/2 x pi x D

      Perimeter of semicircle = 1/2 x pi x D + D

      Given perimeter of semicircle = 61.68, we can say:

      1/2 x pi x D + D = 61.68

      1/2 x 3.14 x D + D =61.68

      1.57D+D= 61.68

      D x (1.57+1)= 61.68

      D x 2.57= 61.68

      D = 61.68/2.57

      D= 24

      To check,

      Sub D = 24 into 1/2 x 3.14 x D +D

      1/2 x 3.14 x 24 + 24

      Perimeter:

       1.57 x 24 + 24

       37.68 + 24

      = 61.68

       

      CORRECT!

       

      Edited by MyPillowTalks 09 Aug `08, 12:23PM
  • MyPillowTalks
    MyPillowTalks's Avatar
    15,791 posts since Nov '06
  • Maith
    Maith's Avatar
    2,695 posts since Dec '07
  • a-Lost-9uY
    a-Lost-9uY's Avatar
    5,134 posts since Sep '06
  • bonkysleuth
    bonkysleuth's Avatar
    314 posts since Mar '07
    • 10 Aug `08, 11:51AM
      Originally posted by Maith:

      walao,pri 6 got this alr ar?


      i remember vividly learning this when i was in primary 6.

  • maurizio13
    maurizio13's Avatar
    12,343 posts since Sep '06
    • 10 Aug `08, 12:04PM

      Perimeter of Semi-circle = 61.68

      Circumference of Circle = 2(61.68 - 2R)

      **Because the perimeter includes the diameter of the semi-circle (2 x R)

       

      2(pi)R = 2(61.68 - 2R)

      3.14R = 61.68 - 2R

      5.14R = 61.68

      R = 12

       

      Therefore diameter of circle is twice of radius, which means D = 2 x 12 = 24

       

      Edited by maurizio13 10 Aug `08, 12:08PM
  • Chunghong2004
    Chunghong2004's Avatar
    60 posts since Feb '08
Please Login or Signup to reply.