Home / 312-688

Finding the Third Proportional to 312 and 688

Calculator

Solution

The third proportional to 312 and 688 is: 1,517.13

Step by Step Solution

  1. Step 1: Write the proportion equation
    312 : 688 = 688 : x
  2. Step 2: Convert to fraction form
    312/688 = 688/x
  3. Step 3: Cross multiply
    312x = 688 × 688
  4. Step 4: Simplify right side
    312x = 473,344
  5. Step 5: Solve for x
    x = 473,344/312
  6. Step 6: Final answer
    x = 1,517.13

Related Problems

Find third proportional to 156 and 344
Half scale
Find third proportional to 624 and 1,376
Double scale
Find third proportional to 314 and 692
Similar ratio
Find third proportional to 468 and 1,032
1.5x scale

Why These Related Problems?

These problems maintain the same ratio (2.21) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.