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Finding the Fourth Proportional to 685.53, 945.90 and 390.78

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Solution

The fourth proportional to 685.53, 945.90 and 390.78 is: 539.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    685.53 : 945.90 = 390.78 : x
  2. Step 2: Convert to fraction form
    685.53/945.90 = 390.78/x
  3. Step 3: Cross multiply
    685.53x = 945.90 × 390.78
  4. Step 4: Simplify right side
    685.53x = 369,638.80
  5. Step 5: Solve for x
    x = 369,638.80/685.53
  6. Step 6: Final answer
    x = 539.20

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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.