Question

14. Find the third term, when the other proportions are 2 and 3 (continued proportion).


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Answer 1

The third proportional of two numbers a and b is defined to be that number c such that a : b = b : c. So you want to find a number c such that 12 : 18 = 18 : c. That number is 27. If BD = AC, then the 3rd proportional to AB and AC is CE.