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Finding the Fourth Proportional to 870.61, 1,305 and 639.15

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Solution

The fourth proportional to 870.61, 1,305 and 639.15 is: 958.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    870.61 : 1,305 = 639.15 : x
  2. Step 2: Convert to fraction form
    870.61/1,305 = 639.15/x
  3. Step 3: Cross multiply
    870.61x = 1,305 × 639.15
  4. Step 4: Simplify right side
    870.61x = 834,090.75
  5. Step 5: Solve for x
    x = 834,090.75/870.61
  6. Step 6: Final answer
    x = 958.05

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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.