Improvement made to calculating circumference by string method?

• A. Avoid parallax error
• B. Repeats and average
• C. Thinner string
• D. Parallel winding of springs

Answer: (B)

The main idea here is reducing random measurement errors by repeating the measurement and averaging the results. When you use a string to measure circumference, small, unpredictable mistakes can occur each time—how taut the string is, slight slippage, or reading the ruler at an angle (parallax). If you do the measurement just once, these random errors can bias the result. But by taking several independent measurements and averaging them, those small errors tend to cancel out, giving a value closer to the true circumference.

Other options don’t address this broader way to improve accuracy. A thinner string doesn’t fix the underlying measurement uncertainties and can introduce other issues like snapping or stretching. Avoiding parallax error helps readings, but it’s still just a single measurement; averaging multiple measurements is more robust. Parallel winding of springs isn’t related to this method at all.