IGCSE Maths Rounding and Bounds Questions and Answers
Rounding and Bounds questions with full solutions for Pearson Edexcel International GCSE Mathematics A (4MA1), Higher tier. Read the 4 worked examples first, then cover each solution and redo it yourself.
Rounding, estimation & standard form: Rounding to decimal places or significant figures and writing large/small numbers in standard form.
Rounding Numbers and Using a Calculator: Rounding to sig figs / d.p. and using GDC modes.
Upper and Lower Bounds 1: Error bounds on rounded measurements.
Upper and Lower Bounds 2: Bounds in calculations (area, speed).
Rounding and Bounds worked examples
Worked example 1: Estimating
Estimate the value of \(\dfrac{48.7\times9.12}{0.31}\).
Solution
Round each number to 1 significant figure: \(50\), \(9\), \(0.3\).
\(50\times9=450\).
\(450\div0.3=4500\div3=1500\).
Answer: 1500
Tip: Dividing by 0.3 makes the answer bigger.
Worked example 2: Calculator work and rounding
Work out \(\dfrac{\sqrt{12.5}+3.1^2}{4.7}\), giving your answer to 3 significant figures.
Solution
\(\sqrt{12.5}=3.5355\ldots\) and \(3.1^2=9.61\).
Numerator: \(13.1455\ldots\).
Divide by 4.7: \(2.79692\ldots\).
To 3 s.f.: 2.80.
Answer: 2.80
Tip: Keep full calculator values until the final step; the zero in 2.80 is significant.
Worked example 3: Bounds
A length is 6.4 m to 1 decimal place. Write down its lower and upper bounds.
Solution
Half of 0.1 is 0.05.
Lower bound 6.35 m, upper bound 6.45 m.
Answer: 6.35 m and 6.45 m
Tip: The upper bound is not included, but is used in calculations.
Worked example 4: Bounds in a subtraction
\(a=12\) to the nearest integer and \(b=4.3\) to 1 d.p. Find the upper bound of \(a-b\).
Solution
For the largest difference use the largest \(a\) and smallest \(b\).
\(12.5-4.25=8.25\).
Answer: 8.25
Tip: For subtraction and division, pair an upper bound with a lower bound.
Every question and worked example here is original, written for IGCSE Math Revision rather than copied from Pearson papers, and each answer was re-solved independently before publishing.
Which Edexcel IGCSE Maths papers test rounding and bounds?
Either Higher tier paper, 1H or 2H, can test rounding and bounds: both cover the whole Pearson Edexcel International GCSE Mathematics A (4MA1) specification and both allow a calculator. Show your method, because most marks are for working.
Where can I practise more rounding and bounds questions?
In the IGCSE student hub: Unit 1 (Number) has more exam-style questions on this topic, each with a mark scheme. Practice starts with a 7-day free trial; the worked examples and questions on this page are free.
IGCSE Math Revision