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Finding the Fourth Proportional to 21, 31.28 and 19.46

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Solution

The fourth proportional to 21, 31.28 and 19.46 is: 28.99

Step by Step Solution

  1. Step 1: Write the proportion equation
    21 : 31.28 = 19.46 : x
  2. Step 2: Convert to fraction form
    21/31.28 = 19.46/x
  3. Step 3: Cross multiply
    21x = 31.28 × 19.46
  4. Step 4: Simplify right side
    21x = 608.71
  5. Step 5: Solve for x
    x = 608.71/21
  6. Step 6: Final answer
    x = 28.99

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Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.