Without working out the exact answer, explain how you can tell that Katie's answer must be wrong.
1 mark
Show answer
6.2 x 48.9 is roughly 6 x 50 = 300, so the answer should be close to 300, not close to 3000. Katie's answer is about ten times too big.
2
Work out an estimate for the value of
48.7 × 6.120.216
You must round each number to 1 significant figure.
3 marks
Show answer
1500
3
41,872 fans attend a rugby match.
Round 41,872 to the nearest 1000
Each fan pays £5 for a match programme.
Use your answer to part (a) to work out an estimate for the total amount paid for programmes.
3 marks
Show answer
a) 42,000b) £210,000
4
Work out an estimate for 62.3 × 4.87
You are given that 623 × 487 = 303,401
Use this fact to write down the exact value of 62.3 × 4.87
3 marks
Show answer
a) 300b) 303.401
5
Marco is building a fence.
He buys 28 fence panels costing £19.75 each.
He also buys a tin of paint costing £41.80
By rounding each number to 1 significant figure, work out an estimate for the total amount Marco pays.
4 marks
Show answer
£640
6
A lorry driver has to drive 289 miles from Leeds to Plymouth.
Her average speed for the journey is 48 miles per hour.
Work out an estimate for the time the journey takes.
Round both numbers to 1 significant figure before calculating.
4 marks
Show answer
6 hours
7
Amara drives 189 km at an average speed of 62 km/h.
By rounding both numbers to 1 significant figure, work out an estimate for the time her journey takes.
Give your answer in hours and minutes.
Is your answer to part (a) an underestimate or an overestimate of the actual time?
Give a reason for your answer.
4 marks
Show answer
a) 3 hours 20 minutesb) Overestimate, because the distance was rounded up and the speed was rounded down
8
Dan is walking a long-distance path that is 990 km long.
He walks at an average speed of 4.8 km/h for 8 hours each day.
By rounding each number to 1 significant figure, work out an estimate for the number of days Dan takes to walk the whole path.
4 marks
Show answer
25 days
9
A rectangular floor is 4.2 m long and 3.1 m wide.
Flooring costs £24.60 per square metre.
By rounding each number to 1 significant figure, work out an estimate for the cost of flooring for the whole floor.
Is your answer to part (a) an underestimate or an overestimate of the actual cost?
Give a reason for your answer.
4 marks
Show answer
a) £240b) Underestimate, because every number was rounded down
10
A square field has an area of 7900 m²
Work out an estimate for the length of one side of the field.
You must show your working and explain how you know your estimate is sensible.
4 marks
Show answer
About 89 m. The side length is the square root of 7900. Since 80 squared = 6400 and 90 squared = 8100, the side is between 80 m and 90 m, and because 7900 is very close to 8100 the side is close to 90 m - about 89 m (89 squared = 7921).
11
Work out an estimate for the value of 9.72 × 5.30.48
Given that 1.84 = 10.4976, write down the value of 184
Write down the value of 5−2
4 marks
Show answer
a) 100b) 104,976c) 1/25
12
One evening a theatre sells 412 adult tickets and 243 child tickets.
An adult ticket costs £11.75
A child ticket costs £5.20
By rounding each number to 1 significant figure, work out an estimate for the total amount of money the theatre takes from ticket sales.
Is your answer to part (a) an underestimate or an overestimate of the actual amount?
Give a reason for your answer.
6 marks
Show answer
a) £5,000b) Underestimate, because every number was rounded down
13
Write the number 4738 correct to 2 significant figures.
Write the number 0.05372 correct to 2 significant figures.
2 marks
Show answer
a) 4700b) 0.054
Every question here is original and written by Robinson Tuition. The grade follows the Edexcel grade descriptors and suits AQA and OCR too; this is not an exam-board paper.