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Finding the Fourth Proportional to 1,128.72, 1,557.80 and 815

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Solution

The fourth proportional to 1,128.72, 1,557.80 and 815 is: 1,124.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,128.72 : 1,557.80 = 815 : x
  2. Step 2: Convert to fraction form
    1,128.72/1,557.80 = 815/x
  3. Step 3: Cross multiply
    1,128.72x = 1,557.80 × 815
  4. Step 4: Simplify right side
    1,128.72x = 1,269,607
  5. Step 5: Solve for x
    x = 1,269,607/1,128.72
  6. Step 6: Final answer
    x = 1,124.82

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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.