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Finding the Fourth Proportional to 971.60, 1,339.21 and 687.65

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Solution

The fourth proportional to 971.60, 1,339.21 and 687.65 is: 947.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    971.60 : 1,339.21 = 687.65 : x
  2. Step 2: Convert to fraction form
    971.60/1,339.21 = 687.65/x
  3. Step 3: Cross multiply
    971.60x = 1,339.21 × 687.65
  4. Step 4: Simplify right side
    971.60x = 920,904.32
  5. Step 5: Solve for x
    x = 920,904.32/971.60
  6. Step 6: Final answer
    x = 947.82

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.