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Finding the Fourth Proportional to 420.80, 631.29 and 128.28

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Solution

The fourth proportional to 420.80, 631.29 and 128.28 is: 192.45

Step by Step Solution

  1. Step 1: Write the proportion equation
    420.80 : 631.29 = 128.28 : x
  2. Step 2: Convert to fraction form
    420.80/631.29 = 128.28/x
  3. Step 3: Cross multiply
    420.80x = 631.29 × 128.28
  4. Step 4: Simplify right side
    420.80x = 80,984.01
  5. Step 5: Solve for x
    x = 80,984.01/420.80
  6. Step 6: Final answer
    x = 192.45

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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.