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Finding the Fourth Proportional to 782.40, 1,081.80 and 685.20

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Solution

The fourth proportional to 782.40, 1,081.80 and 685.20 is: 947.40

Step by Step Solution

  1. Step 1: Write the proportion equation
    782.40 : 1,081.80 = 685.20 : x
  2. Step 2: Convert to fraction form
    782.40/1,081.80 = 685.20/x
  3. Step 3: Cross multiply
    782.40x = 1,081.80 × 685.20
  4. Step 4: Simplify right side
    782.40x = 741,249.36
  5. Step 5: Solve for x
    x = 741,249.36/782.40
  6. Step 6: Final answer
    x = 947.40

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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.