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Finding the Fourth Proportional to 21, 31.50 and 7.47

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Solution

The fourth proportional to 21, 31.50 and 7.47 is: 11.20

Step by Step Solution

  1. Step 1: Write the proportion equation
    21 : 31.50 = 7.47 : x
  2. Step 2: Convert to fraction form
    21/31.50 = 7.47/x
  3. Step 3: Cross multiply
    21x = 31.50 × 7.47
  4. Step 4: Simplify right side
    21x = 235.13
  5. Step 5: Solve for x
    x = 235.13/21
  6. Step 6: Final answer
    x = 11.20

Related Problems

Find fourth proportional to 10.50, 15.75 and 3.73
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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.