Question

if R resistance is divided into 5 equal parts and connected them into series then calculate total resistance

Answer 1

if you know the following two formula its basic maths left 
in case of series connected resistances
 

in case of parallel connected resistors  



Here Rseries = 9 and Rparallel = 2

so 

Rs=9=R1+R2                 eqn 1
Rp=1/2=(1/R1)+(1/R2)    eqn 2

solving eqn 2 
2= R1*R2/(R1 + R2)
giving 18/R2= R1

putting it in eq1  and solving gives 

R1= 6 and R2=3