Dehydrobromination of 3-bromo-3-cyclopentylhexane and number of possible alkene products
The structures (i) and (ii) have two isomers each,namely E and Z isomers.

For the structure (iii) there is a plane of symmetry (marked in the diagram) so it is not a geometrical isomer.

Thus Number of isomers=2 (of structure i) +2 (of structure        ii) + 1(of structure iii)= 5 isomers