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Finding the Fourth Proportional to 1,985.79, 2,978.64 and 687.22

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Solution

The fourth proportional to 1,985.79, 2,978.64 and 687.22 is: 1,030.82

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,985.79 : 2,978.64 = 687.22 : x
  2. Step 2: Convert to fraction form
    1,985.79/2,978.64 = 687.22/x
  3. Step 3: Cross multiply
    1,985.79x = 2,978.64 × 687.22
  4. Step 4: Simplify right side
    1,985.79x = 2,046,980.98
  5. Step 5: Solve for x
    x = 2,046,980.98/1,985.79
  6. Step 6: Final answer
    x = 1,030.82

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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.