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Finding the Fourth Proportional to 1,125.20, 1,686.20 and 987.60

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Solution

The fourth proportional to 1,125.20, 1,686.20 and 987.60 is: 1,480.00

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,125.20 : 1,686.20 = 987.60 : x
  2. Step 2: Convert to fraction form
    1,125.20/1,686.20 = 987.60/x
  3. Step 3: Cross multiply
    1,125.20x = 1,686.20 × 987.60
  4. Step 4: Simplify right side
    1,125.20x = 1,665,291.12
  5. Step 5: Solve for x
    x = 1,665,291.12/1,125.20
  6. Step 6: Final answer
    x = 1,480.00

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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.