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Finding the Fourth Proportional to 1,187.12, 1,780.92 and 639.60

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Solution

The fourth proportional to 1,187.12, 1,780.92 and 639.60 is: 959.53

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,187.12 : 1,780.92 = 639.60 : x
  2. Step 2: Convert to fraction form
    1,187.12/1,780.92 = 639.60/x
  3. Step 3: Cross multiply
    1,187.12x = 1,780.92 × 639.60
  4. Step 4: Simplify right side
    1,187.12x = 1,139,076.43
  5. Step 5: Solve for x
    x = 1,139,076.43/1,187.12
  6. Step 6: Final answer
    x = 959.53

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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.