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Finding the Fourth Proportional to 685.31, 945.90 and 390.74

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Solution

The fourth proportional to 685.31, 945.90 and 390.74 is: 539.32

Step by Step Solution

  1. Step 1: Write the proportion equation
    685.31 : 945.90 = 390.74 : x
  2. Step 2: Convert to fraction form
    685.31/945.90 = 390.74/x
  3. Step 3: Cross multiply
    685.31x = 945.90 × 390.74
  4. Step 4: Simplify right side
    685.31x = 369,596.24
  5. Step 5: Solve for x
    x = 369,596.24/685.31
  6. Step 6: Final answer
    x = 539.32

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Half scale
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Double scale
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1.5x scale

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.