Home › RRB NTPC › Quantitative Aptitude › Ratio and Proportion › Find the fourth proportional to $4$, $9$ and $12$.
Find the fourth proportional to $4$, $9$ and $12$.
A$18$
B$21$
C$24$
D$27$
Answer & Solution
Correct answer: D. $27$
If $4 : 9 = 12 : x$, then by the product-of-means equals product-of-extremes rule, $4x = 9 \times 12 = 108$, so $x = 27$.
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