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Finding the Fourth Proportional to 1,985.76, 2,979.20 and 687.36

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Solution

The fourth proportional to 1,985.76, 2,979.20 and 687.36 is: 1,031.23

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,985.76 : 2,979.20 = 687.36 : x
  2. Step 2: Convert to fraction form
    1,985.76/2,979.20 = 687.36/x
  3. Step 3: Cross multiply
    1,985.76x = 2,979.20 × 687.36
  4. Step 4: Simplify right side
    1,985.76x = 2,047,782.91
  5. Step 5: Solve for x
    x = 2,047,782.91/1,985.76
  6. Step 6: Final answer
    x = 1,031.23

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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.