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Finding the Fourth Proportional to 810.40, 1,214.80 and 420.60

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Solution

The fourth proportional to 810.40, 1,214.80 and 420.60 is: 630.48

Step by Step Solution

  1. Step 1: Write the proportion equation
    810.40 : 1,214.80 = 420.60 : x
  2. Step 2: Convert to fraction form
    810.40/1,214.80 = 420.60/x
  3. Step 3: Cross multiply
    810.40x = 1,214.80 × 420.60
  4. Step 4: Simplify right side
    810.40x = 510,944.88
  5. Step 5: Solve for x
    x = 510,944.88/810.40
  6. Step 6: Final answer
    x = 630.48

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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.