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Finding the Fourth Proportional to 39, 58.50 and 21

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Solution

The fourth proportional to 39, 58.50 and 21 is: 31.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    39 : 58.50 = 21 : x
  2. Step 2: Convert to fraction form
    39/58.50 = 21/x
  3. Step 3: Cross multiply
    39x = 58.50 × 21
  4. Step 4: Simplify right side
    39x = 1,228.40
  5. Step 5: Solve for x
    x = 1,228.40/39
  6. Step 6: Final answer
    x = 31.50

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.