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Finding the Fourth Proportional to 840.90, 1,261.07 and 407.78

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Solution

The fourth proportional to 840.90, 1,261.07 and 407.78 is: 611.53

Step by Step Solution

  1. Step 1: Write the proportion equation
    840.90 : 1,261.07 = 407.78 : x
  2. Step 2: Convert to fraction form
    840.90/1,261.07 = 407.78/x
  3. Step 3: Cross multiply
    840.90x = 1,261.07 × 407.78
  4. Step 4: Simplify right side
    840.90x = 514,239.12
  5. Step 5: Solve for x
    x = 514,239.12/840.90
  6. Step 6: Final answer
    x = 611.53

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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.