Here is an octagonal spinner (Fig A). 1, 2, 3, 4, 5, 6, 7, and 8 are 
marked on it. Write the probabilities of occurrence of the following 
events. 


a Spinner lands on 4. P(4) = 
b Spinner lands on an even number. P(even) 
c Spinner lands on ten. P(10) = 
d Spinner lands on a number less than 4. 
P(less than 4) = 
e P(less than 9) = 
f P(3 to 6)- 

Dear Student,
$Probability=\frac{Favourable number of outcomes}{Total number of outcomes}$
In the given question, Since there are  8 possibilities when we spin the wheel, Total no. of outcomes=8
(a)Favourable no. of outcomes = 1 (Since only one portion is marked 4)
 $\Rightarrow P\left(4\right)=\frac{1}{8}$
(b)Favourable no. of outcomes = 4 (Since there are four portions marked with an even number , namely, 2,4,6,8)

$\Rightarrow P\left(even\right)=\frac{4}{8}=\frac{1}{2}$
(c)Favourable no. of outcomes=0 (Since there is no potion marked with 10)
 $\Rightarrow P\left(10\right)=\frac{0}{8}=0$
(d)Favourable no. of outcomes= 3 (Since there are 3 numbers less than 4 namely 1,2,3)

$\Rightarrow P(less than 4)=\frac{3}{8}$
(e)Favourable no. of outcomes=8 (Since all numbers are less than 9)
$\Rightarrow P(less than 9)=\frac{8}{8}=1$
(f) Favourable no. of outcomes=4 (i.e. 3,4,5,6)
$\Rightarrow P(3 to 6)=\frac{4}{8}=\frac{1}{2}$
Regards