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Finding the Fourth Proportional to 928.80, 1,387.80 and 890.40

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Solution

The fourth proportional to 928.80, 1,387.80 and 890.40 is: 1,330.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    928.80 : 1,387.80 = 890.40 : x
  2. Step 2: Convert to fraction form
    928.80/1,387.80 = 890.40/x
  3. Step 3: Cross multiply
    928.80x = 1,387.80 × 890.40
  4. Step 4: Simplify right side
    928.80x = 1,235,697.12
  5. Step 5: Solve for x
    x = 1,235,697.12/928.80
  6. Step 6: Final answer
    x = 1,330.42

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.