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Finding the Fourth Proportional to 990.21, 1,485.77 and 405.65

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Solution

The fourth proportional to 990.21, 1,485.77 and 405.65 is: 608.65

Step by Step Solution

  1. Step 1: Write the proportion equation
    990.21 : 1,485.77 = 405.65 : x
  2. Step 2: Convert to fraction form
    990.21/1,485.77 = 405.65/x
  3. Step 3: Cross multiply
    990.21x = 1,485.77 × 405.65
  4. Step 4: Simplify right side
    990.21x = 602,693.14
  5. Step 5: Solve for x
    x = 602,693.14/990.21
  6. Step 6: Final answer
    x = 608.65

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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.