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Finding the Fourth Proportional to 685.18, 945.64 and 390.47

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Solution

The fourth proportional to 685.18, 945.64 and 390.47 is: 538.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    685.18 : 945.64 = 390.47 : x
  2. Step 2: Convert to fraction form
    685.18/945.64 = 390.47/x
  3. Step 3: Cross multiply
    685.18x = 945.64 × 390.47
  4. Step 4: Simplify right side
    685.18x = 369,244.05
  5. Step 5: Solve for x
    x = 369,244.05/685.18
  6. Step 6: Final answer
    x = 538.90

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Double scale
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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.