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Finding the Fourth Proportional to 870.86, 1,305.37 and 639.40

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Solution

The fourth proportional to 870.86, 1,305.37 and 639.40 is: 958.42

Step by Step Solution

  1. Step 1: Write the proportion equation
    870.86 : 1,305.37 = 639.40 : x
  2. Step 2: Convert to fraction form
    870.86/1,305.37 = 639.40/x
  3. Step 3: Cross multiply
    870.86x = 1,305.37 × 639.40
  4. Step 4: Simplify right side
    870.86x = 834,653.58
  5. Step 5: Solve for x
    x = 834,653.58/870.86
  6. Step 6: Final answer
    x = 958.42

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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.