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Finding the Fourth Proportional to 42.90, 64.28 and 31.56

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Solution

The fourth proportional to 42.90, 64.28 and 31.56 is: 47.28

Step by Step Solution

  1. Step 1: Write the proportion equation
    42.90 : 64.28 = 31.56 : x
  2. Step 2: Convert to fraction form
    42.90/64.28 = 31.56/x
  3. Step 3: Cross multiply
    42.90x = 64.28 × 31.56
  4. Step 4: Simplify right side
    42.90x = 2,028.52
  5. Step 5: Solve for x
    x = 2,028.52/42.90
  6. Step 6: Final answer
    x = 47.28

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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.