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Finding the Fourth Proportional to 39, 53.78 and 31.70

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Solution

The fourth proportional to 39, 53.78 and 31.70 is: 43.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    39 : 53.78 = 31.70 : x
  2. Step 2: Convert to fraction form
    39/53.78 = 31.70/x
  3. Step 3: Cross multiply
    39x = 53.78 × 31.70
  4. Step 4: Simplify right side
    39x = 1,704.83
  5. Step 5: Solve for x
    x = 1,704.83/39
  6. Step 6: Final answer
    x = 43.71

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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.