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Finding the Fourth Proportional to 905, 1,248.90 and 491

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Solution

The fourth proportional to 905, 1,248.90 and 491 is: 677.58

Step by Step Solution

  1. Step 1: Write the proportion equation
    905 : 1,248.90 = 491 : x
  2. Step 2: Convert to fraction form
    905/1,248.90 = 491/x
  3. Step 3: Cross multiply
    905x = 1,248.90 × 491
  4. Step 4: Simplify right side
    905x = 613,209.90
  5. Step 5: Solve for x
    x = 613,209.90/905
  6. Step 6: Final answer
    x = 677.58

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.