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Finding the Fourth Proportional to 1,115, 1,672.50 and 431

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Solution

The fourth proportional to 1,115, 1,672.50 and 431 is: 646.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,115 : 1,672.50 = 431 : x
  2. Step 2: Convert to fraction form
    1,115/1,672.50 = 431/x
  3. Step 3: Cross multiply
    1,115x = 1,672.50 × 431
  4. Step 4: Simplify right side
    1,115x = 720,847.50
  5. Step 5: Solve for x
    x = 720,847.50/1,115
  6. Step 6: Final answer
    x = 646.50

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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.