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# C1 watch

1. 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.
2. 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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3. 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
4. (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.
5. (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!
6. (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
7. (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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8. (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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