Find the fourth proportional to 5, 8, and 15.
Aptitude
Ratio and Proportion
Difficulty: Easy
Choose an option
Answer
Correct Answer: 24
Explanation
Problem restatementFor numbers a : b = c : x, find x with a = 5, b = 8, c = 15.
Concept/ApproachFourth proportional x satisfies 5 : 8 = 15 : x ⇒ x = (8 × 15) ÷ 5.
Step-by-step calculation x = (8 × 15) ÷ 5 = 120 ÷ 5 = 24
Verification/Alternative5 : 8 = 15 : 24 → both ratios equal 5÷8 = 0.625 and 15÷24 = 0.625.
Final Answer24