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Finding the Fourth Proportional to 21, 31.50 and 11.50

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Solution

The fourth proportional to 21, 31.50 and 11.50 is: 17.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    21 : 31.50 = 11.50 : x
  2. Step 2: Convert to fraction form
    21/31.50 = 11.50/x
  3. Step 3: Cross multiply
    21x = 31.50 × 11.50
  4. Step 4: Simplify right side
    21x = 362.25
  5. Step 5: Solve for x
    x = 362.25/21
  6. Step 6: Final answer
    x = 17.25

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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.