Find the fourth proportional to 12, 16 and 18.
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 24
The fourth proportional to \(a,\ b,\ c\) is the number \(d\) with \(a:b=c:d\), so \(\displaystyle d=\frac{b\times c}{a}\).
\(12:16=18:d\)
\(\displaystyle d=\frac{16\times18}{12}=\frac{288}{12}=24\)
The fourth proportional is 24.