The physics
A spring pulls back with F = k x. A hanging mass stops where k x = m g.
in a line (series): 1/k = 1/k₁ + 1/k₂ side by side (parallel): k = k₁ + k₂
In a line, every spring carries the whole load. The stretches add. Side by side, every spring stretches the same amount. The forces add.
Cut a spring, and k × length stays the same. So a shorter piece is stiffer.
a piece 1/n as long has n k
In a lift, use g + a when the acceleration points up. Use g − a when it points down.