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Finding the Fourth Proportional to 815.80, 1,223.70 and 621.40

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Solution

The fourth proportional to 815.80, 1,223.70 and 621.40 is: 932.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    815.80 : 1,223.70 = 621.40 : x
  2. Step 2: Convert to fraction form
    815.80/1,223.70 = 621.40/x
  3. Step 3: Cross multiply
    815.80x = 1,223.70 × 621.40
  4. Step 4: Simplify right side
    815.80x = 760,407.18
  5. Step 5: Solve for x
    x = 760,407.18/815.80
  6. Step 6: Final answer
    x = 932.10

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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.