What a rounded number really means

Mathematics · Number Representation & Place Value · ages 15-16

Name ______________________ Date ____________

A length is 7.2 cm to 1 decimal place. What is its lower bound in cm?
Answer: ______________
A length is 12.4 cm to 1 decimal place. What are its bounds?
- 12.35 cm to 12.45 cm
- 12.3 cm to 12.5 cm
- 12.4 cm to 12.5 cm
- 12.35 cm to 12.44 cm
A length is 12.4 cm to 1 decimal place. What are its bounds?
- 12.35 cm to 12.45 cm
- 12.3 cm to 12.5 cm
- 12.4 cm to 12.5 cm
For 6.5 kg to 1 decimal place, the error interval includes 6.55.
Circle one: True False
A length is 8.6 cm to 1 decimal place. What is its upper bound in cm?
Answer: ______________
A mass is 340 g to the nearest 10 g. What could it really be?
- 330 g to 340 g
- 340 g to 350 g
- 335 g to 345 g
Which error interval matches 12.4 cm to 1 decimal place?
- 12.35 < x ≤ 12.45
- 12.3 < x < 12.5
- 12.35 ≤ x < 12.45
- 12.35 ≤ x ≤ 12.45
Maya says the upper bound is included in the error interval. Is Maya right?
Circle one: True False
Which inequality matches 4.27 to 2 decimal places?
- 4.26 <= x < 4.28
- 4.265 <= x < 4.275
- 4.27 <= x < 4.28
A mass is 1200 g to the nearest 100 g. What is its lower bound in g?
Answer: ______________

Answer key

For grown-ups. Fold this page away before handing over the rest.

7.15 · 7.2 minus 0.05 = 7.15.
12.35 cm to 12.45 cm · Half of 0.1 is 0.05 each way. The 12.3 to 12.5 option uses a whole step.
12.35 cm to 12.45 cm · Half of 0.1 is 0.05 each way: 12.35 up to 12.45.
False · The upper bound stays out with <, so 6.55 is not included.
8.65 · 8.6 plus 0.05 = 8.65.
335 g to 345 g · Half step 5 g each way: 335 up to but not including 345.
12.35 ≤ x < 12.45 · Lower bound joins in, upper stays out. The flipped-signs option reverses the convention.
False · The upper bound is strict: values stop just below it.
4.265 <= x < 4.275 · Half of 0.01 is 0.005 each way, lower inclusive.
1150 · 1200 minus 50 = 1150.