History of Hindu Mathematics: A Source Book v1.c8.s12.47

v1.c8.s12.47

**Inverse Rule of Three.** The Hindu name for the Inverse Rule of Three is *vyasta-trairāśika* (lit. "inverse rule of three terms"). After describing the method of the Rule of Three the Hindu writers remark that the operation should be reversed when the proportion is inverse. Thus Śrīdhara observes: