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Finding the Fourth Proportional to 991.80, 1,487.78 and 261.38

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Solution

The fourth proportional to 991.80, 1,487.78 and 261.38 is: 392.08

Step by Step Solution

  1. Step 1: Write the proportion equation
    991.80 : 1,487.78 = 261.38 : x
  2. Step 2: Convert to fraction form
    991.80/1,487.78 = 261.38/x
  3. Step 3: Cross multiply
    991.80x = 1,487.78 × 261.38
  4. Step 4: Simplify right side
    991.80x = 388,868.17
  5. Step 5: Solve for x
    x = 388,868.17/991.80
  6. Step 6: Final answer
    x = 392.08

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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.