Question

How many people can sit on a tendon bicycle at a time​

Answer 1

It is sometimes single or sometime dual as well. It depends on the type of it.

Answer 2

Tandems can have more than two riders – tandem refers to the arrangement of the riders one behind the other rather than the number of riders. Bicycles for three, four, or five riders are referred to as "triples" or "triplets", "quads" or "quadruplets", and "quints" or "quintuplets" respectively

Most tandems have two seats, one behind the other, although there are versions with three seats (called a triplet) or even more. The front rider, called the pilot or captain, controls the steering, the brakes and the gears. The rear rider, called the stoker, helps to pedal.