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Finding the Fourth Proportional to 685.20, 945.60 and 390.42

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Solution

The fourth proportional to 685.20, 945.60 and 390.42 is: 538.79

Step by Step Solution

  1. Step 1: Write the proportion equation
    685.20 : 945.60 = 390.42 : x
  2. Step 2: Convert to fraction form
    685.20/945.60 = 390.42/x
  3. Step 3: Cross multiply
    685.20x = 945.60 × 390.42
  4. Step 4: Simplify right side
    685.20x = 369,181.15
  5. Step 5: Solve for x
    x = 369,181.15/685.20
  6. Step 6: Final answer
    x = 538.79

Related Problems

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Half scale
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Double scale
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Similar ratio
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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.