9 jumps 
but on the last jump he will be on the top 

This Is a Certified Answer

Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
Height of the pole : 10 m.  jump amount each attempt:  2 m. 
slipping amount each time:  1 m.

the jump      height      slipped        final
number       reached    height        position
 1                 2m         1m            1 m
2                  3m          1m            2m
8                 9m            1m            8m
9                 10m 

Thus after the 9th attempt/jump, the spider reaches the top of the pole/roof.  Since it goes to the horizontal position, spider does not slip down.
from the first two attempts/jumps, we see that the spider's final position N meters is equal to the number of jumps N.

we need to find when the spider attains 10 m (target height) - 2 m (jumping height) = 8 meters.  Because, from 8 m  the spider can reach the top and stay there without slipping.

So to attain 8 m (after slipping), it takes 8 attempts.  In the 9th attempt, the spider goes to the top.

2 5 2