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Finding the Fourth Proportional to 1,187.77, 1,780.83 and 639.40

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Solution

The fourth proportional to 1,187.77, 1,780.83 and 639.40 is: 958.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,187.77 : 1,780.83 = 639.40 : x
  2. Step 2: Convert to fraction form
    1,187.77/1,780.83 = 639.40/x
  3. Step 3: Cross multiply
    1,187.77x = 1,780.83 × 639.40
  4. Step 4: Simplify right side
    1,187.77x = 1,138,662.70
  5. Step 5: Solve for x
    x = 1,138,662.70/1,187.77
  6. Step 6: Final answer
    x = 958.66

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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.