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Finding the Fourth Proportional to 990.42, 1,365.27 and 780.21

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Solution

The fourth proportional to 990.42, 1,365.27 and 780.21 is: 1,075.50

Step by Step Solution

  1. Step 1: Write the proportion equation
    990.42 : 1,365.27 = 780.21 : x
  2. Step 2: Convert to fraction form
    990.42/1,365.27 = 780.21/x
  3. Step 3: Cross multiply
    990.42x = 1,365.27 × 780.21
  4. Step 4: Simplify right side
    990.42x = 1,065,197.31
  5. Step 5: Solve for x
    x = 1,065,197.31/990.42
  6. Step 6: Final answer
    x = 1,075.50

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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.