Find the fourth proportional to 3, 4 and 9.
12
If \(a:b::c:d\), then \(d\) is called the fourth proportional to \(a, b, c\) and satisfies \(\dfrac{a}{b}=\dfrac{c}{d}\), which gives \(d=\dfrac{b\times c}{a}\).
Taking \(a=3\), \(b=4\), \(c=9\), the fourth proportional is \(d=\dfrac{4\times 9}{3}=\dfrac{36}{3}=12\). Hence, 12.
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Important Questions from Fourth Proportional
Find the fourth proportional of (x4 - y4), (x + y) and (x − y), provided x ≠ y.
What is the fourth proportional to the numbers 8, 66 and 112?
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Find the fourth proportion of the following numbers.
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