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Finding the Fourth Proportional to 21.80, 30.28 and 21.12

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Solution

The fourth proportional to 21.80, 30.28 and 21.12 is: 29.34

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.80 : 30.28 = 21.12 : x
  2. Step 2: Convert to fraction form
    21.80/30.28 = 21.12/x
  3. Step 3: Cross multiply
    21.80x = 30.28 × 21.12
  4. Step 4: Simplify right side
    21.80x = 639.51
  5. Step 5: Solve for x
    x = 639.51/21.80
  6. Step 6: Final answer
    x = 29.34

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1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.39) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.