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Finding the Fourth Proportional to 678.78, 1,017.42 and 313.20

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Solution

The fourth proportional to 678.78, 1,017.42 and 313.20 is: 469.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    678.78 : 1,017.42 = 313.20 : x
  2. Step 2: Convert to fraction form
    678.78/1,017.42 = 313.20/x
  3. Step 3: Cross multiply
    678.78x = 1,017.42 × 313.20
  4. Step 4: Simplify right side
    678.78x = 318,655.94
  5. Step 5: Solve for x
    x = 318,655.94/678.78
  6. Step 6: Final answer
    x = 469.45

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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.