Truncating
I can estimate a value by truncating to a given degree of accuracy.
Lesson details
Key learning points
- When estimating ages, it is convention to use truncation.
- Truncation can be used to estimate any integer to a given accuracy.
- Truncation can be used to estimate any number to a given accuracy.
Keywords
Truncate - Truncation is the simplifying a number by 'cutting off' one or more of the digits and replacing them with zeros if necessary to preserve place value.
A degree of accuracy - A degree of accuracy shows how precise a number or measurement is.
Common misconception
When truncating, pupils are tempted to round. Also, when truncating, they cut off the number without thinking about the magnitude.
The use of the place value table shows the magnitude of the number, thus preserving their place value when truncating.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.__________ shows how precise a number or measurement is.
Q2.Match each number to its rounded value.
323 -
320 (2 s.f.)
294.82 -
294.8 (1 d.p.)
291 -
290 (2 s.f.)
294.829 -
294.83 (2 d.p.)
Q3.A square plot of grass has a length of 2.89 m to 2 decimal places. Select the correct estimate for the area of the square grass plot.
Q4.Match each number to its rounded value.
0.0038903 -
0.0039 (2 s.f.)
0.038903 -
0.04 (2 d.p.)
0.00038903 -
0.0004 (1 s.f.)
0.000038903 -
0.000039 (2 s.f.)
Q5.Which of the following are correct, quick estimate calculations for $${4.56\times8.95} \over {0.498}$$?
Q6.Match each calculation to its correct approximate answer.
$${19.89} \over {0.498}$$ -
$$\approx 40$$
$${19.89} \over {0.2134}$$ -
$$\approx 100$$
$${19.89} \over {0.1111}$$ -
$$\approx 200$$
$${19.89} \over {2.073}$$ -
$$\approx 10$$
Assessment exit quiz
6 Questions
Q1.__________ is the simplifying a number by 'cutting off' one or more of the digits and replacing them with zeros if necessary to preserve place value.
Q2.Match each number with its truncated value to 1 significant figure.
46 347 823 -
40 000 000
4634 -
4000
46.347 -
40
46 347.823 -
40 000
4.634823 -
4
Q3.Truncate 49.999999 to 3 significant figures. Select the correct response.
Q4.Jacob thinks of a number. Truncated to 1 s.f. Jun's number is 100. Jun's number is a multiple of 8 and it is 105 when rounded to the nearest 5.
Q5.Match the appropriate treatment of the answer (exact, rounded to truncated) to each context.
Exact answer is required -
A length of wood 37 m needs to be cut into 5 equal strips.
Rounded answer is required -
A meal is £37 and you share it between 5 people and want to give a tip
Truncated answer is required -
You have £37 and want to buy as many £5 puzzle cubes as possible.
Q6.In computer science, ‘INT’ or ‘int’ is used to truncate a number so to only give the integers. For example, INT(56/10) has an output of 5. Match each computer instruction to its output.
INT(78/8) -
9
INT(90/8) -
11
INT(123/10) + INT(7.9/3) -
14
INT(789/10) + INT(56/3) -
96
INT(1.65/10) + INT(76.6/3) -
25
INT(8/0.5) + INT(12.65/2) − INT(9.8/6) -
21