Mathematics for IGCSE & O level - Proportion (Section 1 - No. 41)

If *a* varies jointly as *b* and *c*, which equation represents the relationship, where *k* is the constant of proportionality?

*a* = k*b/c

*a* = k*b*c

*a* = k*b + c

*a* = k*c/b

Joint variation means a variable is proportional to the product of two or more other variables. Thus, a = kbc.