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Finding the Fourth Proportional to 1,120.75, 1,680.72 and 390.13

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Solution

The fourth proportional to 1,120.75, 1,680.72 and 390.13 is: 585.05

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,120.75 : 1,680.72 = 390.13 : x
  2. Step 2: Convert to fraction form
    1,120.75/1,680.72 = 390.13/x
  3. Step 3: Cross multiply
    1,120.75x = 1,680.72 × 390.13
  4. Step 4: Simplify right side
    1,120.75x = 655,699.29
  5. Step 5: Solve for x
    x = 655,699.29/1,120.75
  6. Step 6: Final answer
    x = 585.05

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Double scale
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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.