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Finding the Fourth Proportional to 1,312.80, 1,811.87 and 781.71

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Solution

The fourth proportional to 1,312.80, 1,811.87 and 781.71 is: 1,078.88

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,312.80 : 1,811.87 = 781.71 : x
  2. Step 2: Convert to fraction form
    1,312.80/1,811.87 = 781.71/x
  3. Step 3: Cross multiply
    1,312.80x = 1,811.87 × 781.71
  4. Step 4: Simplify right side
    1,312.80x = 1,416,356.90
  5. Step 5: Solve for x
    x = 1,416,356.90/1,312.80
  6. Step 6: Final answer
    x = 1,078.88

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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.