This deep dive covers Finding Bounds within Bounds & Error Intervals for GCSE Mathematics. Revise Bounds & Error Intervals in Number for GCSE Mathematics with 14 exam-style questions and 5 flashcards. This is a high-frequency topic, so it is worth revising until the explanation feels precise and repeatable. It is section 3 of 7 in this topic. Use this deep dive to connect the idea to the wider topic before moving on to questions and flashcards.
Finding Bounds
1
Identify the degree of accuracy (1 d.p., nearest 10, etc.)
2
Find HALF the accuracy interval
3
LB = value − half interval, UB = value + half interval
| Rounded to... | Half interval | Example: 50 |
|---|---|---|
| Nearest whole number | ±0.5 | LB=49.5, UB=50.5 |
| 1 decimal place | ±0.05 | LB=49.95, UB=50.05 |
| Nearest 10 | ±5 | LB=45, UB=55 |
| Nearest 100 | ±50 | LB=0 (can't go negative if context), UB=100 |
Practice questions for Bounds & Error Intervals
A length is 240 cm to the nearest 10 cm. What is the lower bound of the length?
A mass m is 45 kg to the nearest kilogram. Write down the error interval for m using inequality notation.
Quick recall flashcards
Max of A ÷ B
Max = UB(A) ÷ LB(B). Big top, small bottom = big answer
Rationalising
Remove surd from denominator: 1/√2 = √2/2