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Finding the Fourth Proportional to 1,391.90, 2,087.21 and 417.80

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Solution

The fourth proportional to 1,391.90, 2,087.21 and 417.80 is: 626.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,391.90 : 2,087.21 = 417.80 : x
  2. Step 2: Convert to fraction form
    1,391.90/2,087.21 = 417.80/x
  3. Step 3: Cross multiply
    1,391.90x = 2,087.21 × 417.80
  4. Step 4: Simplify right side
    1,391.90x = 872,023.81
  5. Step 5: Solve for x
    x = 872,023.81/1,391.90
  6. Step 6: Final answer
    x = 626.50

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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.