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Finding the Fourth Proportional to 780.40, 1,076.34 and 485.56

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Solution

The fourth proportional to 780.40, 1,076.34 and 485.56 is: 669.69

Step by Step Solution

  1. Step 1: Write the proportion equation
    780.40 : 1,076.34 = 485.56 : x
  2. Step 2: Convert to fraction form
    780.40/1,076.34 = 485.56/x
  3. Step 3: Cross multiply
    780.40x = 1,076.34 × 485.56
  4. Step 4: Simplify right side
    780.40x = 522,627.65
  5. Step 5: Solve for x
    x = 522,627.65/780.40
  6. Step 6: Final answer
    x = 669.69

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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.