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Finding the Fourth Proportional to 1,128.90, 1,557.90 and 686.70

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Solution

The fourth proportional to 1,128.90, 1,557.90 and 686.70 is: 947.66

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,128.90 : 1,557.90 = 686.70 : x
  2. Step 2: Convert to fraction form
    1,128.90/1,557.90 = 686.70/x
  3. Step 3: Cross multiply
    1,128.90x = 1,557.90 × 686.70
  4. Step 4: Simplify right side
    1,128.90x = 1,069,809.93
  5. Step 5: Solve for x
    x = 1,069,809.93/1,128.90
  6. Step 6: Final answer
    x = 947.66

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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.