iGCSE Mathematics (0580) - C1.10 Limits of accuracy- Exam Style Questions Paper 3- New Syllabus
▶️ Answer/Explanation
(a)
Find the Lowest Common Multiple (LCM) of $20$ and $35$.
Multiples of 20: $20, 40, 60, 80, 100, 120, 140$
Multiples of 35: $35, 70, 105, 140$
The LCM is $140$ minutes, which is $2$ hours and $20$ minutes.
Add this to $09:30$: $09:30 + 2:20 = 11:50$.
✅ Answer: $11:50$
(b)
The distance is rounded to the nearest kilometre, meaning the limit is $\pm 0.5$ km.
Lower bound = $97 – 0.5 = 96.5$
Upper bound = $97 + 0.5 = 97.5$
✅ Answer: $96.5 \le d < 97.5$
▶️ Answer/Explanation
The measurement is given correct to the nearest $1 \text{ m}$. To find the bounds, divide this degree of accuracy by $2$: $1 \text{ m} / 2 = 0.5 \text{ m}$.
Subtract this from the measured value to get the lower bound: $105 – 0.5 = 104.5$.
Add this to the measured value to get the upper bound: $105 + 0.5 = 105.5$.
✅ Answer: $104.5 \le h < 105.5$
Subtract this from the measured value to get the lower bound: $105 – 0.5 = 104.5$.
Add this to the measured value to get the upper bound: $105 + 0.5 = 105.5$.
✅ Answer: $104.5 \le h < 105.5$