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Finding the Fourth Proportional to 810.91, 1,215.66 and 420.69

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Solution

The fourth proportional to 810.91, 1,215.66 and 420.69 is: 630.67

Step by Step Solution

  1. Step 1: Write the proportion equation
    810.91 : 1,215.66 = 420.69 : x
  2. Step 2: Convert to fraction form
    810.91/1,215.66 = 420.69/x
  3. Step 3: Cross multiply
    810.91x = 1,215.66 × 420.69
  4. Step 4: Simplify right side
    810.91x = 511,419.78
  5. Step 5: Solve for x
    x = 511,419.78/810.91
  6. Step 6: Final answer
    x = 630.67

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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.