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Finding the Fourth Proportional to 1,187.12, 1,780.68 and 638.55

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Solution

The fourth proportional to 1,187.12, 1,780.68 and 638.55 is: 957.83

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,187.12 : 1,780.68 = 638.55 : x
  2. Step 2: Convert to fraction form
    1,187.12/1,780.68 = 638.55/x
  3. Step 3: Cross multiply
    1,187.12x = 1,780.68 × 638.55
  4. Step 4: Simplify right side
    1,187.12x = 1,137,055.61
  5. Step 5: Solve for x
    x = 1,137,055.61/1,187.12
  6. Step 6: Final answer
    x = 957.83

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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.