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Finding the Fourth Proportional to 788.10, 1,085.31 and 639.60

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Solution

The fourth proportional to 788.10, 1,085.31 and 639.60 is: 880.81

Step by Step Solution

  1. Step 1: Write the proportion equation
    788.10 : 1,085.31 = 639.60 : x
  2. Step 2: Convert to fraction form
    788.10/1,085.31 = 639.60/x
  3. Step 3: Cross multiply
    788.10x = 1,085.31 × 639.60
  4. Step 4: Simplify right side
    788.10x = 694,164.28
  5. Step 5: Solve for x
    x = 694,164.28/788.10
  6. Step 6: Final answer
    x = 880.81

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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.