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Finding the Fourth Proportional to 1,428.80, 1,972.08 and 987.20

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Solution

The fourth proportional to 1,428.80, 1,972.08 and 987.20 is: 1,362.57

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,428.80 : 1,972.08 = 987.20 : x
  2. Step 2: Convert to fraction form
    1,428.80/1,972.08 = 987.20/x
  3. Step 3: Cross multiply
    1,428.80x = 1,972.08 × 987.20
  4. Step 4: Simplify right side
    1,428.80x = 1,946,837.38
  5. Step 5: Solve for x
    x = 1,946,837.38/1,428.80
  6. Step 6: Final answer
    x = 1,362.57

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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.