Proportion and Its Types

04 Try it yourself Interactive

One chain, three missing-term questions

Set three terms. The walkthrough runs the cross-product test on a : b :: b : c, then computes the mean proportional between the outer two, the third proportional to the first two, and the fourth proportional to all three — and finishes by showing whether the three numbers really form one geometric chain.

4 : 6 :: 6 : 9 — the lesson chain

mean 6 · third 9 · fourth 13.5 · step 3/2

Try 12, 21, 8: the cross-product test fails, so the mean proportional does not come back as 21 — but the fourth proportional is still a clean 14, because that formula never assumed a chain.

Press Next to work through it one step at a time.

Mean prop–

Third prop–

Fourth prop–

Chain step–

step 0 / 0