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Finding the Fourth Proportional to 1,125.78, 1,686.06 and 987.40

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Solution

The fourth proportional to 1,125.78, 1,686.06 and 987.40 is: 1,478.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,125.78 : 1,686.06 = 987.40 : x
  2. Step 2: Convert to fraction form
    1,125.78/1,686.06 = 987.40/x
  3. Step 3: Cross multiply
    1,125.78x = 1,686.06 × 987.40
  4. Step 4: Simplify right side
    1,125.78x = 1,664,815.64
  5. Step 5: Solve for x
    x = 1,664,815.64/1,125.78
  6. Step 6: Final answer
    x = 1,478.81

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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.