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Finding the Fourth Proportional to 790.40, 1,185.60 and 405.76

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Solution

The fourth proportional to 790.40, 1,185.60 and 405.76 is: 608.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    790.40 : 1,185.60 = 405.76 : x
  2. Step 2: Convert to fraction form
    790.40/1,185.60 = 405.76/x
  3. Step 3: Cross multiply
    790.40x = 1,185.60 × 405.76
  4. Step 4: Simplify right side
    790.40x = 481,069.06
  5. Step 5: Solve for x
    x = 481,069.06/790.40
  6. Step 6: Final answer
    x = 608.64

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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.