Math Is Fun Forum

Daniel123

Member

Registered: 2007-05-23

Posts: 663

Arithmetic Series

Does anyone mind checking my answers for these, please?

Propsectors 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 £11 300

b) The total sum of money available for drilling is £76 000. Find, to the nearest 50m, the greatest depth that can be drilled.

Thanks.

Last edited by Daniel123 (2007-09-13 05:50:09)

JaneFairfax

Member

Registered: 2007-02-23

Posts: 6,868

Re: Arithmetic Series

This is slightly wrong. You forgot to divide by 2.

This should give n ≈ 30.02. So the deepest the company can afford to drill is 1500 metres (and this will cost them £75900).

Daniel123

Member

Registered: 2007-05-23

Posts: 663

Re: Arithmetic Series

Woops.

Thank you once again