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Finding the Fourth Proportional to 690.78, 1,037.50 and 665.40

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Solution

The fourth proportional to 690.78, 1,037.50 and 665.40 is: 999.38

Step by Step Solution

  1. Step 1: Write the proportion equation
    690.78 : 1,037.50 = 665.40 : x
  2. Step 2: Convert to fraction form
    690.78/1,037.50 = 665.40/x
  3. Step 3: Cross multiply
    690.78x = 1,037.50 × 665.40
  4. Step 4: Simplify right side
    690.78x = 690,352.50
  5. Step 5: Solve for x
    x = 690,352.50/690.78
  6. Step 6: Final answer
    x = 999.38

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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.