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Finding the Fourth Proportional to 21, 31.50 and 8.18

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Solution

The fourth proportional to 21, 31.50 and 8.18 is: 12.26

Step by Step Solution

  1. Step 1: Write the proportion equation
    21 : 31.50 = 8.18 : x
  2. Step 2: Convert to fraction form
    21/31.50 = 8.18/x
  3. Step 3: Cross multiply
    21x = 31.50 × 8.18
  4. Step 4: Simplify right side
    21x = 257.47
  5. Step 5: Solve for x
    x = 257.47/21
  6. Step 6: Final answer
    x = 12.26

Related Problems

Find fourth proportional to 10.50, 15.75 and 4.09
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Double scale
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Similar ratio
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1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.