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Finding the Fourth Proportional to 31, 42.80 and 21.16

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Solution

The fourth proportional to 31, 42.80 and 21.16 is: 29.21

Step by Step Solution

  1. Step 1: Write the proportion equation
    31 : 42.80 = 21.16 : x
  2. Step 2: Convert to fraction form
    31/42.80 = 21.16/x
  3. Step 3: Cross multiply
    31x = 42.80 × 21.16
  4. Step 4: Simplify right side
    31x = 905.65
  5. Step 5: Solve for x
    x = 905.65/31
  6. Step 6: Final answer
    x = 29.21

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1.5x scale

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.