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Finding the Fourth Proportional to 815.95, 1,125.70 and 639.60

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Solution

The fourth proportional to 815.95, 1,125.70 and 639.60 is: 882.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    815.95 : 1,125.70 = 639.60 : x
  2. Step 2: Convert to fraction form
    815.95/1,125.70 = 639.60/x
  3. Step 3: Cross multiply
    815.95x = 1,125.70 × 639.60
  4. Step 4: Simplify right side
    815.95x = 719,997.72
  5. Step 5: Solve for x
    x = 719,997.72/815.95
  6. Step 6: Final answer
    x = 882.40

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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.