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Finding the Fourth Proportional to 685.18, 945.40 and 390.39

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Solution

The fourth proportional to 685.18, 945.40 and 390.39 is: 538.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    685.18 : 945.40 = 390.39 : x
  2. Step 2: Convert to fraction form
    685.18/945.40 = 390.39/x
  3. Step 3: Cross multiply
    685.18x = 945.40 × 390.39
  4. Step 4: Simplify right side
    685.18x = 369,074.71
  5. Step 5: Solve for x
    x = 369,074.71/685.18
  6. Step 6: Final answer
    x = 538.65

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.