Finding the Fourth Proportional to 138.12, 207.10 and 81
Calculator
Solution
The fourth proportional to 138.12, 207.10 and 81 is: 121.45
Step by Step Solution
- Step 1: Write the proportion equation
138.12 : 207.10 = 81 : x - Step 2: Convert to fraction form
138.12/207.10 = 81/x - Step 3: Cross multiply
138.12x = 207.10 × 81 - Step 4: Simplify right side
138.12x = 16,775.10 - Step 5: Solve for x
x = 16,775.10/138.12 - Step 6: Final answer
x = 121.45
Related Problems
Find fourth proportional to 69.06, 103.55 and 40.50
Half scale
Find fourth proportional to 276.24, 414.20 and 162
Double scale
Find fourth proportional to 139.12, 208.60 and 82
Similar ratio
Find fourth proportional to 207.18, 310.65 and 121.50
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.