Home / 78-121

Finding the Third Proportional to 78 and 121

Calculator

Solution

The third proportional to 78 and 121 is: 187.71

Step by Step Solution

  1. Step 1: Write the proportion equation
    78 : 121 = 121 : x
  2. Step 2: Convert to fraction form
    78/121 = 121/x
  3. Step 3: Cross multiply
    78x = 121 × 121
  4. Step 4: Simplify right side
    78x = 14,641
  5. Step 5: Solve for x
    x = 14,641/78
  6. Step 6: Final answer
    x = 187.71

Related Problems

Find third proportional to 39 and 60.50
Half scale
Find third proportional to 156 and 242
Double scale
Find third proportional to 80 and 124
Similar ratio
Find third proportional to 117 and 181.50
1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.55) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.