Two children play an "incy-wincy" spider game.

They take it in turns to each roll two

dice and move their spiders up their drainpipes as follows:

Score

Movement

2, 3 or 4

5, 6 or 7

8, 9 or 10

11 or 12

Down 1

Stay same

Up 1

Up 2

(i)

Using a normal approximation, calculate the probability that after 15 turns a

child's spider will have moved up more than 8 squares from the start.

[5]

(ii)

Comment briefly on the suitability of this approximation.

[1]

[Total 6]