Results 1 to 3 of 3

Math Help - average problem

  1. #1
    Member
    Joined
    Jan 2008
    Posts
    173

    average problem

    Five students took a mathematics test. The average mark was 68. If the marks of four boys were 75, 62, 74, and 63, the mark of the fifth boy was:

    a. 66 b. 68 c. 76 d. 56 e. None of these
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Moo
    Moo is offline
    A Cute Angle Moo's Avatar
    Joined
    Mar 2008
    From
    P(I'm here)=1/3, P(I'm there)=t+1/3
    Posts
    5,618
    Thanks
    6
    Hello,

    Let x be the mark of the fifth student.
    The definition of "average" is "sum of all marks divided by the number of marks".

    This means that if the average is X, we have :

    \frac{\text{1st mark + 2nd mark + 3rd mark + 4th mark + 5th mark}}{5}=X

    Now you know 4 of the 5 marks and you know the average mark. What equation are you going to solve ?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Apr 2008
    Posts
    65
    (75 + 62 + 74 + 63 + x) / 5 = 68

    (274 + x) / 5 = 68

    274 + x = 340
    x = 340 -274

    x = 66

    plug 66 in for x in the original equation to check
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 5
    Last Post: May 26th 2011, 05:11 AM
  2. Replies: 2
    Last Post: March 13th 2010, 04:49 AM
  3. average value problem
    Posted in the Calculus Forum
    Replies: 3
    Last Post: September 11th 2009, 02:06 PM
  4. Average Problem
    Posted in the Algebra Forum
    Replies: 4
    Last Post: June 2nd 2008, 03:07 PM
  5. average problem
    Posted in the Algebra Forum
    Replies: 8
    Last Post: April 23rd 2008, 10:10 AM

Search Tags


/mathhelpforum @mathhelpforum