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Finding the Fourth Proportional to 780.54, 1,170.64 and 390.39

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Solution

The fourth proportional to 780.54, 1,170.64 and 390.39 is: 585.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    780.54 : 1,170.64 = 390.39 : x
  2. Step 2: Convert to fraction form
    780.54/1,170.64 = 390.39/x
  3. Step 3: Cross multiply
    780.54x = 1,170.64 × 390.39
  4. Step 4: Simplify right side
    780.54x = 457,006.15
  5. Step 5: Solve for x
    x = 457,006.15/780.54
  6. Step 6: Final answer
    x = 585.50

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Double scale
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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.