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Finding the Fourth Proportional to 1,287.70, 1,776.20 and 790.16

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Solution

The fourth proportional to 1,287.70, 1,776.20 and 790.16 is: 1,089.91

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,287.70 : 1,776.20 = 790.16 : x
  2. Step 2: Convert to fraction form
    1,287.70/1,776.20 = 790.16/x
  3. Step 3: Cross multiply
    1,287.70x = 1,776.20 × 790.16
  4. Step 4: Simplify right side
    1,287.70x = 1,403,469.36
  5. Step 5: Solve for x
    x = 1,403,469.36/1,287.70
  6. Step 6: Final answer
    x = 1,089.91

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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.