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Finding the Fourth Proportional to 1,187.58, 1,780.60 and 640.15

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Solution

The fourth proportional to 1,187.58, 1,780.60 and 640.15 is: 959.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,187.58 : 1,780.60 = 640.15 : x
  2. Step 2: Convert to fraction form
    1,187.58/1,780.60 = 640.15/x
  3. Step 3: Cross multiply
    1,187.58x = 1,780.60 × 640.15
  4. Step 4: Simplify right side
    1,187.58x = 1,139,856.25
  5. Step 5: Solve for x
    x = 1,139,856.25/1,187.58
  6. Step 6: Final answer
    x = 959.82

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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.