IGCSE Mathematics | Practice Test | 25 Questions
What does “rounding to 2 decimal places” mean?
State the rounding rule. When do you round up, and when do you round down?
What is a significant figure? State where you start counting from.
Do leading zeros count as significant figures? Give an example to support your answer.
Round $6.473$ to 1 decimal place.
Round $6.473$ to 2 decimal places.
Round $8300$ to 1 significant figure.
Round $0.0052$ to 1 significant figure.
What symbol is used to show an approximate or estimated value?
When estimating a calculation, what do you do to each number before you calculate?
Round $12.485$ to 2 decimal places.
Round $9.996$ to 2 decimal places.
Round $47\,620$ to 2 significant figures.
Round $0.003\,847$ to 2 significant figures.
By rounding each number to 1 significant figure, estimate the value of:
$$\frac{41.3}{9.79 \times 0.765}$$
By rounding each number to 1 significant figure, estimate the value of:
$$\frac{52.4 \times 3.86}{19.3}$$
By rounding each number to 1 significant figure, estimate the value of:
$$\frac{28.9 + 6.85}{0.472}$$
A market stall sells 28 items at \$8.95 each. Estimate the total income.
A swimming pool is $23.8\text{ m}$ long and $11.4\text{ m}$ wide. Calculate the area of the pool. Give your answer to a reasonable degree of accuracy.
A car travels $186\text{ km}$ in $2.4$ hours. Calculate the average speed in km/h. Give your answer to a reasonable degree of accuracy.
(a) Round $0.04567$ to 1 significant figure.
(b) Round $0.04567$ to 2 significant figures.
(c) Round $0.04567$ to 3 significant figures.
(d) Which of your three answers is the most accurate? Explain why.
A student says: “I rounded $7.45$ to 1 decimal place and got $7.5$.”
(a) Is the student correct? Show your working.
(b) Now round $7.45$ to 1 significant figure. Show your working.
(c) Explain why rounding to 1 decimal place and rounding to 1 significant figure give different answers for this number.
A car uses $6.8$ litres of fuel per $100\text{ km}$.
(a) Estimate how much fuel the car uses for a journey of $247\text{ km}$. Show your rounding and working clearly.
(b) Fuel costs \$1.89 per litre. Using your answer to (a), estimate the total cost of fuel for the journey.
(c) Give the cost from (b) to a reasonable degree of accuracy. Explain your choice.
A triangle has base $8.3\text{ cm}$ and height $5.7\text{ cm}$, both measured to the nearest millimetre.
(a) Calculate the area of the triangle. Use the formula $\text{Area} = \dfrac{1}{2} \times \text{base} \times \text{height}$. Show all working.
(b) Give your answer to a reasonable degree of accuracy. Explain your choice.
(c) A student writes: “The area is exactly $23.655\text{ cm}^2$.” Explain why this statement is not appropriate.
A number is $8.745$.
(a) Round $8.745$ directly to 1 decimal place.
(b) A student first rounds $8.745$ to 2 decimal places, then rounds that result to 1 decimal place. Show both steps clearly.
(c) The two methods give different answers. Explain which method is correct, and why the other method gives a wrong result.
