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Finding the Fourth Proportional to 991.15, 1,485.70 and 405.90

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Solution

The fourth proportional to 991.15, 1,485.70 and 405.90 is: 608.43

Step by Step Solution

  1. Step 1: Write the proportion equation
    991.15 : 1,485.70 = 405.90 : x
  2. Step 2: Convert to fraction form
    991.15/1,485.70 = 405.90/x
  3. Step 3: Cross multiply
    991.15x = 1,485.70 × 405.90
  4. Step 4: Simplify right side
    991.15x = 603,045.63
  5. Step 5: Solve for x
    x = 603,045.63/991.15
  6. Step 6: Final answer
    x = 608.43

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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.