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Finding the Fourth Proportional to 31.02, 42.80 and 21.80

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Solution

The fourth proportional to 31.02, 42.80 and 21.80 is: 30.08

Step by Step Solution

  1. Step 1: Write the proportion equation
    31.02 : 42.80 = 21.80 : x
  2. Step 2: Convert to fraction form
    31.02/42.80 = 21.80/x
  3. Step 3: Cross multiply
    31.02x = 42.80 × 21.80
  4. Step 4: Simplify right side
    31.02x = 933.04
  5. Step 5: Solve for x
    x = 933.04/31.02
  6. Step 6: Final answer
    x = 30.08

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.