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Finding the Fourth Proportional to 1,421.42, 2,130.74 and 728.40

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Solution

The fourth proportional to 1,421.42, 2,130.74 and 728.40 is: 1,091.90

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,421.42 : 2,130.74 = 728.40 : x
  2. Step 2: Convert to fraction form
    1,421.42/2,130.74 = 728.40/x
  3. Step 3: Cross multiply
    1,421.42x = 2,130.74 × 728.40
  4. Step 4: Simplify right side
    1,421.42x = 1,552,038.10
  5. Step 5: Solve for x
    x = 1,552,038.10/1,421.42
  6. Step 6: Final answer
    x = 1,091.90

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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.