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Leaving Cert Algebra Q

  • 12-02-2013 12:44pm
    #1
    dtfo
    Registered Users, Registered Users 2 Posts: 125 ✭✭


    This is a question from my Leaving cert Maths book, any help would be gratefully appreciated:D

    The relationship between degrees Fahrenheit(F) and degrees Celsius(C) is given by the formula F=9/5C +32

    At what temperature will degrees Celsius be twice degrees Fahrenheit


Comments

  • #2
    Bobsammy
    Registered Users, Registered Users 2 Posts: 356 ✭✭Bobsammy


    You need to think about the relationship between Celsius and Fahrenheit, if Celsius is twice the degrees Fahrenheit then C = 2F.

    Think about what you could do with that information.


  • #3
    dtfo
    Registered Users, Registered Users 2 Posts: 125 ✭✭dtfo


    Ye I substituted that in the formula but ending up getting that F=-12.3 and C=-24.6 , is that still twice even though its negative? Maybe I dont understand it correctly


  • #4
    Bobsammy
    Registered Users, Registered Users 2 Posts: 356 ✭✭Bobsammy


    Those answers sound spot on.


  • #5
    Yakuza
    Registered Users, Registered Users 2 Posts: 5,141 ✭✭✭Yakuza


    Those answers are fine. Twice a negative number is a bigger negative number (i.e further away from zero!)
    As a total aside - see what you get when you put -40 for C into your F = 9/5 * C + 32 :)


  • #6
    dtfo
    Registered Users, Registered Users 2 Posts: 125 ✭✭dtfo


    Yakuza wrote: »
    Those answers are fine. Twice a negative number is a bigger negative number (i.e further away from zero!)
    As a total aside - see what you get when you put -40 for C into your F = 9/5 * C + 32 :)

    Thanks thats exactly where my problem was.

    The first part of the question was actually find the value where Fahrenheit and Celsius are the same value :)


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