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Finding the Fourth Proportional to 1,289.78, 1,779.20 and 1,113.47

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Solution

The fourth proportional to 1,289.78, 1,779.20 and 1,113.47 is: 1,535.98

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,289.78 : 1,779.20 = 1,113.47 : x
  2. Step 2: Convert to fraction form
    1,289.78/1,779.20 = 1,113.47/x
  3. Step 3: Cross multiply
    1,289.78x = 1,779.20 × 1,113.47
  4. Step 4: Simplify right side
    1,289.78x = 1,981,080.26
  5. Step 5: Solve for x
    x = 1,981,080.26/1,289.78
  6. Step 6: Final answer
    x = 1,535.98

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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.