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Finding the Fourth Proportional to 1,221.72, 1,830.24 and 782.40

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Solution

The fourth proportional to 1,221.72, 1,830.24 and 782.40 is: 1,172.10

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,221.72 : 1,830.24 = 782.40 : x
  2. Step 2: Convert to fraction form
    1,221.72/1,830.24 = 782.40/x
  3. Step 3: Cross multiply
    1,221.72x = 1,830.24 × 782.40
  4. Step 4: Simplify right side
    1,221.72x = 1,431,979.78
  5. Step 5: Solve for x
    x = 1,431,979.78/1,221.72
  6. Step 6: Final answer
    x = 1,172.10

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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.