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Finding the Fourth Proportional to 491.78, 678.36 and 386.70

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Solution

The fourth proportional to 491.78, 678.36 and 386.70 is: 533.41

Step by Step Solution

  1. Step 1: Write the proportion equation
    491.78 : 678.36 = 386.70 : x
  2. Step 2: Convert to fraction form
    491.78/678.36 = 386.70/x
  3. Step 3: Cross multiply
    491.78x = 678.36 × 386.70
  4. Step 4: Simplify right side
    491.78x = 262,320.60
  5. Step 5: Solve for x
    x = 262,320.60/491.78
  6. Step 6: Final answer
    x = 533.41

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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.