Results 1 to 2 of 2

Math Help - Word problem

  1. #1
    Member
    Joined
    Apr 2009
    From
    california
    Posts
    121

    Word problem

    Which of the following pairs of quantities vary directly?

    a. the circumference of a cirlce and the diameter of the circle
    b. the distance traveled in two hours and the average rate of travel
    c.the number of gallons of gasoline bought and the cost of the purchase
    d. the area of a circle and the radius of the circle

    I think it is a,c and d. Is the answer correct?

    Does vary directly mean that it will always be a linear equation?

    Thanks to everyone for helping me and putting up with my random questions. I love doing word problems but I don't know much about algebra yet. so I am just trying to do the ones I can.

    Thanks.

    Vicky
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Grandad's Avatar
    Joined
    Dec 2008
    From
    South Coast of England
    Posts
    2,570
    Thanks
    1
    Hello Vicky
    Quote Originally Posted by Vicky1997 View Post
    Which of the following pairs of quantities vary directly?

    a. the circumference of a cirlce and the diameter of the circle
    b. the distance traveled in two hours and the average rate of travel
    c.the number of gallons of gasoline bought and the cost of the purchase
    d. the area of a circle and the radius of the circle

    I think it is a,c and d. Is the answer correct?

    Does vary directly mean that it will always be a linear equation?

    Thanks to everyone for helping me and putting up with my random questions. I love doing word problems but I don't know much about algebra yet. so I am just trying to do the ones I can.

    Thanks.

    Vicky
    A simple but effective way to test whether two quantities vary directly is this: if I double one quantity, do I double the other quantity? If the answer is yes, then they probably vary directly.

    So (a) If you double the diameter, does the circumference double? Yes. So you're right.

    (b) If you double the average rate of travel (in other words, the speed) does the distance you'll travel in two hours double also? Answer: yes. So you're not right - this does vary directly.

    (c) If you buy twice as much gas, does it cost twice as much? Yes. So you're right here.

    (d) If the radius of a circle is doubled, does the area double? No, it goes up by a factor of 4, because it's proportional to the square of the radius. So, you're not right on this one.

    OK, now?

    Grandad
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. word problem - the snow plough problem?
    Posted in the Differential Equations Forum
    Replies: 1
    Last Post: October 13th 2011, 02:02 PM
  2. Replies: 3
    Last Post: January 2nd 2011, 09:20 PM
  3. 1 Word problem and 1 function problem
    Posted in the Algebra Forum
    Replies: 8
    Last Post: April 21st 2010, 09:01 AM
  4. Replies: 2
    Last Post: January 10th 2009, 06:49 AM

Search Tags


/mathhelpforum @mathhelpforum