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Finding the Fourth Proportional to 870, 1,305 and 859.20

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Solution

The fourth proportional to 870, 1,305 and 859.20 is: 1,288.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    870 : 1,305 = 859.20 : x
  2. Step 2: Convert to fraction form
    870/1,305 = 859.20/x
  3. Step 3: Cross multiply
    870x = 1,305 × 859.20
  4. Step 4: Simplify right side
    870x = 1,121,256
  5. Step 5: Solve for x
    x = 1,121,256/870
  6. Step 6: Final answer
    x = 1,288.80

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Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.