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Finding the Fourth Proportional to 1,405.12, 1,938.96 and 784

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Solution

The fourth proportional to 1,405.12, 1,938.96 and 784 is: 1,081.86

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,405.12 : 1,938.96 = 784 : x
  2. Step 2: Convert to fraction form
    1,405.12/1,938.96 = 784/x
  3. Step 3: Cross multiply
    1,405.12x = 1,938.96 × 784
  4. Step 4: Simplify right side
    1,405.12x = 1,520,144.64
  5. Step 5: Solve for x
    x = 1,520,144.64/1,405.12
  6. Step 6: Final answer
    x = 1,081.86

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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.