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    I just wanted help with a C1 Question I got stuck on.
    Prospectors are drilling for oil. The cost of Drilling to a depth of 50m is £500. To Drill a further 50m costs £640 and, hence, the total cost of drilling to a depth of 100m is £1140. Each subsequent extra depth of 50m costs £140 more to drill than the previous 50m.

    a) Show that the cost of drilling to a depth of 500m is £11300.

    b) The total sum of money available for drilling is £76000. Find, to the nearest 50m, the greatest depth that can be drilled.

    I managed to do part a fairly easily but in part b I ended up with a quadratic that can't be factorised. Any advice would be much appreciated.
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    Have you tried using the quadratic formula? If the factorising is the problem using the formula instead should get you there

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    I ended up with a negative square root which is obviously wrong. Also we are not allowed calculators in c1 so actually using the quadratic formula is very difficult
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    (Original post by (student))
    I just wanted help with a C1 Question I got stuck on.
    Prospectors are drilling for oil. The cost of Drilling to a depth of 50m is £500. To Drill a further 50m costs £640 and, hence, the total cost of drilling to a depth of 100m is £1140. Each subsequent extra depth of 50m costs £140 more to drill than the previous 50m.

    a) Show that the cost of drilling to a depth of 500m is £11300.

    b) The total sum of money available for drilling is £76000. Find, to the nearest 50m, the greatest depth that can be drilled.

    I managed to do part a fairly easily but in part b I ended up with a quadratic that can't be factorised. Any advice would be much appreciated.
    Can you post your working please?
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    (Original post by (student))
    I ended up with a negative square root which is obviously wrong. Also we are not allowed calculators in c1 so actually using the quadratic formula is very difficult
    Is this question from a textbook?

    Some C1 textbooks use old P1 questions where calculators were allowed - you wouldn't get a 'difficult' quadratic in the exam!
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    (Original post by (student))
    I just wanted help with a C1 Question I got stuck on.
    Prospectors are drilling for oil. The cost of Drilling to a depth of 50m is £500. To Drill a further 50m costs £640 and, hence, the total cost of drilling to a depth of 100m is £1140. Each subsequent extra depth of 50m costs £140 more to drill than the previous 50m.

    a) Show that the cost of drilling to a depth of 500m is £11300.

    b) The total sum of money available for drilling is £76000. Find, to the nearest 50m, the greatest depth that can be drilled.

    I managed to do part a fairly easily but in part b I ended up with a quadratic that can't be factorised. Any advice would be much appreciated.
    I might be wrong but I believe that this forms a sequence so I would advise trying the two formulae that you get in C1 for sequences
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    (Original post by (student))
    I just wanted help with a C1 Question I got stuck on.
    Prospectors are drilling for oil. The cost of Drilling to a depth of 50m is £500. To Drill a further 50m costs £640 and, hence, the total cost of drilling to a depth of 100m is £1140. Each subsequent extra depth of 50m costs £140 more to drill than the previous 50m.

    a) Show that the cost of drilling to a depth of 500m is £11300.

    b) The total sum of money available for drilling is £76000. Find, to the nearest 50m, the greatest depth that can be drilled.

    I managed to do part a fairly easily but in part b I ended up with a quadratic that can't be factorised. Any advice would be much appreciated.
    Try completing the square.

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    (Original post by davros)
    Is this question from a textbook?

    Some C1 textbooks use old P1 questions where calculators were allowed - you wouldn't get a 'difficult' quadratic in the exam!
    Yes (it is from a textbook)-that could be why
 
 
 

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