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Finding the Fourth Proportional to 42.90, 64.36 and 21.26

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Solution

The fourth proportional to 42.90, 64.36 and 21.26 is: 31.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    42.90 : 64.36 = 21.26 : x
  2. Step 2: Convert to fraction form
    42.90/64.36 = 21.26/x
  3. Step 3: Cross multiply
    42.90x = 64.36 × 21.26
  4. Step 4: Simplify right side
    42.90x = 1,368.48
  5. Step 5: Solve for x
    x = 1,368.48/42.90
  6. Step 6: Final answer
    x = 31.90

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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.