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Finding the Fourth Proportional to 1,289.90, 1,780.57 and 870.50

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Solution

The fourth proportional to 1,289.90, 1,780.57 and 870.50 is: 1,201.63

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,289.90 : 1,780.57 = 870.50 : x
  2. Step 2: Convert to fraction form
    1,289.90/1,780.57 = 870.50/x
  3. Step 3: Cross multiply
    1,289.90x = 1,780.57 × 870.50
  4. Step 4: Simplify right side
    1,289.90x = 1,549,986.19
  5. Step 5: Solve for x
    x = 1,549,986.19/1,289.90
  6. Step 6: Final answer
    x = 1,201.63

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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.