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Finding the Fourth Proportional to 21.72, 30 and 21.50

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Solution

The fourth proportional to 21.72, 30 and 21.50 is: 29.70

Step by Step Solution

  1. Step 1: Write the proportion equation
    21.72 : 30 = 21.50 : x
  2. Step 2: Convert to fraction form
    21.72/30 = 21.50/x
  3. Step 3: Cross multiply
    21.72x = 30 × 21.50
  4. Step 4: Simplify right side
    21.72x = 645
  5. Step 5: Solve for x
    x = 645/21.72
  6. Step 6: Final answer
    x = 29.70

Related Problems

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Double scale
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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.