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Math Help - Inequalities and average speeed

  1. #1
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    Inequalities and average speeed

    hello i am in urgent need of help with 2 questions the first one is an inequality

    Find all the integer values of n which satisfy

    -15 < 5n <= 20

    and the second one may sound stupid but i couldnt get it

    anna drove 35 miles from southhampton to basingstoke

    she drove at an average speed of 20 mph for the first 5 miles
    and then an average speed of 60 mps for the remaining 30 miles

    calculate her average speed for the whole journey.

    plz help and if you say how you got would be better thanks!
    Last edited by Anthony bailey; January 9th 2008 at 11:12 AM.
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by Anthony bailey View Post
    hello i am in urgent need of help with 2 questions the first one is an inequality

    Find all the integer values of n which satisfy

    -15 < 5n same as or equal to 20
    i have no idea what you are trying to say here

    and the second one may sound stupid but i couldnt get it

    anna drove 35 miles from southhampton to basingstoke

    she drove at an average speed of 20 mph for the first 5 miles
    and then an average speed of 60 mps for the remaining 30 miles

    calculate her average speed for the whole journey.

    plz help and if you say how you got would be better thanks!
    recall, \mbox{Speed} = \frac {\mbox{Distance}}{\mbox{Time}}

    we know the distance, now we need to find the time. (here, of course, i'm talking about average speed, total distance, and total time)

    the time we are looking for will be the sum of the times for the two parts of the journey. so, how much time did she take to drive the first 5 miles? how much time did she take to drive the last 30 miles? Hint: you can use the same formula i gave you above
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  3. #3
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    nah lol it doesnt tell you the time thats all it says :S
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by Anthony bailey View Post
    nah lol it doesnt tell you the time thats all it says :S
    i know it doesn't tell you the times, there'd be nothing to work out if it did. i wanted you to find the times using the formula i gave you. for example, for the first leg of the journey, you would plug in speed = 20, and distance = 5, and solve for the time. do a similar thing for the second leg. then add the two times you get, and that will be the total time for the trip. then you can use that to find the average speed for the whole journey, again, using the same formula
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  5. #5
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    thanks very much it worked lol i finished it and i was wondering cud any1 help with the inequality one?
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    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by Anthony bailey View Post
    thanks very much it worked lol i finished it and i was wondering cud any1 help with the inequality one?
    just divide through by 5. we get:

    -3 < n \le 4

    what integers fall in that range? list them
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  7. #7
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    thanks very much already had it right tho :s tyvm !!
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