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Finding the Fourth Proportional to 1,405.40, 1,938.94 and 815.80

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Solution

The fourth proportional to 1,405.40, 1,938.94 and 815.80 is: 1,125.51

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,405.40 : 1,938.94 = 815.80 : x
  2. Step 2: Convert to fraction form
    1,405.40/1,938.94 = 815.80/x
  3. Step 3: Cross multiply
    1,405.40x = 1,938.94 × 815.80
  4. Step 4: Simplify right side
    1,405.40x = 1,581,787.25
  5. Step 5: Solve for x
    x = 1,581,787.25/1,405.40
  6. Step 6: Final answer
    x = 1,125.51

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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.