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Finding the Fourth Proportional to 1,121.34, 1,681.68 and 390.78

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Solution

The fourth proportional to 1,121.34, 1,681.68 and 390.78 is: 586.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,121.34 : 1,681.68 = 390.78 : x
  2. Step 2: Convert to fraction form
    1,121.34/1,681.68 = 390.78/x
  3. Step 3: Cross multiply
    1,121.34x = 1,681.68 × 390.78
  4. Step 4: Simplify right side
    1,121.34x = 657,166.91
  5. Step 5: Solve for x
    x = 657,166.91/1,121.34
  6. Step 6: Final answer
    x = 586.05

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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.