Find the fourth proportional to 8, 14 and 20.
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → 35
The fourth proportional to \(a,\ b,\ c\) is the number \(d\) with \(a:b=c:d\), so \(\displaystyle d=\frac{b\times c}{a}\).
\(8:14=20:d\)
\(\displaystyle d=\frac{14\times20}{8}=\frac{280}{8}=35\)
The fourth proportional is 35.