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Finding the Fourth Proportional to 858.90, 1,285.65 and 615.90

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Solution

The fourth proportional to 858.90, 1,285.65 and 615.90 is: 921.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    858.90 : 1,285.65 = 615.90 : x
  2. Step 2: Convert to fraction form
    858.90/1,285.65 = 615.90/x
  3. Step 3: Cross multiply
    858.90x = 1,285.65 × 615.90
  4. Step 4: Simplify right side
    858.90x = 791,831.84
  5. Step 5: Solve for x
    x = 791,831.84/858.90
  6. Step 6: Final answer
    x = 921.91

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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.