Home / 721.89-996.20-390.31

Finding the Fourth Proportional to 721.89, 996.20 and 390.31

Calculator

Solution

The fourth proportional to 721.89, 996.20 and 390.31 is: 538.63

Step by Step Solution

  1. Step 1: Write the proportion equation
    721.89 : 996.20 = 390.31 : x
  2. Step 2: Convert to fraction form
    721.89/996.20 = 390.31/x
  3. Step 3: Cross multiply
    721.89x = 996.20 × 390.31
  4. Step 4: Simplify right side
    721.89x = 388,826.65
  5. Step 5: Solve for x
    x = 388,826.65/721.89
  6. Step 6: Final answer
    x = 538.63

Related Problems

Find fourth proportional to 360.94, 498.10 and 195.16
Half scale
Find fourth proportional to 1,443.77, 1,992.40 and 780.62
Double scale
Find fourth proportional to 722.89, 997.58 and 391.31
Similar ratio
Find fourth proportional to 1,082.83, 1,494.30 and 585.47
1.5x scale

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.