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Finding the Fourth Proportional to 878.64, 1,315.20 and 647.78

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Solution

The fourth proportional to 878.64, 1,315.20 and 647.78 is: 969.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    878.64 : 1,315.20 = 647.78 : x
  2. Step 2: Convert to fraction form
    878.64/1,315.20 = 647.78/x
  3. Step 3: Cross multiply
    878.64x = 1,315.20 × 647.78
  4. Step 4: Simplify right side
    878.64x = 851,960.26
  5. Step 5: Solve for x
    x = 851,960.26/878.64
  6. Step 6: Final answer
    x = 969.64

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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.