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Finding the Fourth Proportional to 721.60, 1,080.96 and 678.40

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Solution

The fourth proportional to 721.60, 1,080.96 and 678.40 is: 1,016.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    721.60 : 1,080.96 = 678.40 : x
  2. Step 2: Convert to fraction form
    721.60/1,080.96 = 678.40/x
  3. Step 3: Cross multiply
    721.60x = 1,080.96 × 678.40
  4. Step 4: Simplify right side
    721.60x = 733,323.26
  5. Step 5: Solve for x
    x = 733,323.26/721.60
  6. Step 6: Final answer
    x = 1,016.25

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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.