Prize Puzzle Competition 30

Closing date is 31st August 2001

88.I have a rule for combining pairs of numbers to make another number
Using that rule:(3, 9) make 18
(5, 8) make 33
(7, 6) make 55
What TWO pairs of numbers will make 17?

89.The numbers 3, 7, 8, 40, 50 and 60 have one property in common which is NOT possessed by any other whole number.
What is that property?

90.Four married couples were sitting around a circular table.
No man was sitting next to his wife or another man.
Mr Coster was not sitting next to Mrs Black.
Mr Black was not sitting next to Mrs Dell.
Moving clockwise around the table, the women were seated in the same order of their names as the men.
Mrs Archer was sitting on the right of Mr Black.
Who was sitting on the right of Mrs. Coster?

The winner of Competition #29 was Nathan Richards of St. Austell, Cornwall.
The answers were:

85.5 ways
86.61 stairs
87.27.5 metres