Two parallel sides of a trapezium are $91$ cm and $51$ cm; the other two sides are $37$ cm and $13$ cm. The perpendicular distance between the parallel sides is —

Dropping perpendiculars from the shorter side splits the base difference $91 - 51 = 40$ cm into two segments. With $h = 12$: $\sqrt{37^2 - 12^2} = 35$ and , and confirms the height is cm.