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Finding the Fourth Proportional to 878.40, 1,316.16 and 390.72

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Solution

The fourth proportional to 878.40, 1,316.16 and 390.72 is: 585.44

Step by Step Solution

  1. Step 1: Write the proportion equation
    878.40 : 1,316.16 = 390.72 : x
  2. Step 2: Convert to fraction form
    878.40/1,316.16 = 390.72/x
  3. Step 3: Cross multiply
    878.40x = 1,316.16 × 390.72
  4. Step 4: Simplify right side
    878.40x = 514,250.04
  5. Step 5: Solve for x
    x = 514,250.04/878.40
  6. Step 6: Final answer
    x = 585.44

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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.