Home / 138.93-208.13-81.15

Finding the Fourth Proportional to 138.93, 208.13 and 81.15

Calculator

Solution

The fourth proportional to 138.93, 208.13 and 81.15 is: 121.57

Step by Step Solution

  1. Step 1: Write the proportion equation
    138.93 : 208.13 = 81.15 : x
  2. Step 2: Convert to fraction form
    138.93/208.13 = 81.15/x
  3. Step 3: Cross multiply
    138.93x = 208.13 × 81.15
  4. Step 4: Simplify right side
    138.93x = 16,889.34
  5. Step 5: Solve for x
    x = 16,889.34/138.93
  6. Step 6: Final answer
    x = 121.57

Related Problems

Find fourth proportional to 69.47, 104.06 and 40.58
Half scale
Find fourth proportional to 277.86, 416.25 and 162.30
Double scale
Find fourth proportional to 139.93, 209.62 and 82.15
Similar ratio
Find fourth proportional to 208.40, 312.19 and 121.73
1.5x scale

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.