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Finding the Fourth Proportional to 840.78, 1,259.46 and 428.70

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Solution

The fourth proportional to 840.78, 1,259.46 and 428.70 is: 642.18

Step by Step Solution

  1. Step 1: Write the proportion equation
    840.78 : 1,259.46 = 428.70 : x
  2. Step 2: Convert to fraction form
    840.78/1,259.46 = 428.70/x
  3. Step 3: Cross multiply
    840.78x = 1,259.46 × 428.70
  4. Step 4: Simplify right side
    840.78x = 539,930.50
  5. Step 5: Solve for x
    x = 539,930.50/840.78
  6. Step 6: Final answer
    x = 642.18

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1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.