a) An offshore oil rig is drilling 1000 metres below the sea bed. Estimate the cost of drilling if the first metre costs £200, with an increase of £22 for each further metre drilled. Here we

a)       An offshore oil rig is drilling 1000 metres below the sea bed. Estimate the cost of drilling if the first metre costs £200, with an increase of £22 for each further metre drilled.

Here we apply arithmetic progression

Where a= 200 (first term)

              d =22  (common difference)

             n = 1000

therefore,

             =       £22,178

b)    The motor powering the drill has 10 speeds. These vary from 10 rpm to 800 rpm. If the speeds are to be in a geometric progression, find the common ratio, and make a table showing the ten required speeds. Round off your answer to the nearest whole number.

800 = 10

80 =

r =

r =  1.63

 = 1.63

No

1

2

3

4

5

6

7

8

9

10

Speed

10

12

27

43

71

115

188

306

498

800