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Finding the Fourth Proportional to 42.80, 64.18 and 21.40

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Solution

The fourth proportional to 42.80, 64.18 and 21.40 is: 32.09

Step by Step Solution

  1. Step 1: Write the proportion equation
    42.80 : 64.18 = 21.40 : x
  2. Step 2: Convert to fraction form
    42.80/64.18 = 21.40/x
  3. Step 3: Cross multiply
    42.80x = 64.18 × 21.40
  4. Step 4: Simplify right side
    42.80x = 1,373.45
  5. Step 5: Solve for x
    x = 1,373.45/42.80
  6. Step 6: Final answer
    x = 32.09

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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.