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Finding the Fourth Proportional to 655.80, 905.20 and 390.43

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Solution

The fourth proportional to 655.80, 905.20 and 390.43 is: 538.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    655.80 : 905.20 = 390.43 : x
  2. Step 2: Convert to fraction form
    655.80/905.20 = 390.43/x
  3. Step 3: Cross multiply
    655.80x = 905.20 × 390.43
  4. Step 4: Simplify right side
    655.80x = 353,417.24
  5. Step 5: Solve for x
    x = 353,417.24/655.80
  6. Step 6: Final answer
    x = 538.91

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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.