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Finding the Fourth Proportional to 990.12, 1,365.74 and 780.08

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Solution

The fourth proportional to 990.12, 1,365.74 and 780.08 is: 1,076.01

Step by Step Solution

  1. Step 1: Write the proportion equation
    990.12 : 1,365.74 = 780.08 : x
  2. Step 2: Convert to fraction form
    990.12/1,365.74 = 780.08/x
  3. Step 3: Cross multiply
    990.12x = 1,365.74 × 780.08
  4. Step 4: Simplify right side
    990.12x = 1,065,379.63
  5. Step 5: Solve for x
    x = 1,065,379.63/990.12
  6. Step 6: Final answer
    x = 1,076.01

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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.