Decimal Places & Significant Figures Round Off Practice 2
This section offers 6 targeted questions to help you master rounding to decimal places and significant figures. Use them to practice, revise, or check your accuracy, and strengthen your understanding of these important techniques.
Related Lessons:
Practice 2 - Question 1
The radius of a plant cell is 0.0003039cm. Express the diameter of the cell to 2 significant figures.
Solution:
Diameter = 0.0006078=0.00061 (2.s.f)
Practice 2 - Question 2
Express 67.4962 correct to two decimal places.
Solution:
Note that for this question, the trailing “0” is significant as we are required to correct the answer to 2 decimal places.
67.4962=67.50 (2d.p.)
Practice 2 - Question 3
If a 3 digit number rounded up to 2 significant figures is 800, and the first 2 digits are 8 and 0 respectively, state all the possible value(s) of the last digit.
Solution:
Now, to solve this question, we need to round off all possibility starting from 800 to 805:
800=800 (2s.f.)
801=800 (2s.f.)
802=800 (2s.f.)
803=800 (2s.f.)
804=800 (2s.f.)
805=810 (2s.f.) ≠800
Therefore, the possible last digits are 0, 1, 2, 3 and 4.
Practice 2 - Question 4
Round off 25487 to 2 significant figures.
Solution:
For this question, the last three digits “000” are significant. A common mistake students make is writing the answer as 25. However, we can clearly see that the value has been reduced that drastically, so 25 cannot be the correct answer.
25487=25000 (2.s.f.)
Practice 2 - Question 5
Evaluate \(\frac{\sqrt8+\left(-3.1\right)^2}{7.02} \)using a calculator, taking the positive square root, rounding off your answer to 2 decimal places.
Solution:
Pressing our calculator, we get the answer 1.7718557. Therefore,
1.7718557 = 1.77 (2d.p.)
Practice 2 - Question 6
The weight of the cupboard is 51.096 kg. Round off the weight to
- 3 significant figures
- 2 decimal places
- nearest integer
Solution:
a) 51.096=51.1 (3s.f.)
b) 51.096=51.10 (2d.p.)
c) 51.096=51 (nearest integer)
Full Solution Step By Step
Here is a full walkthrough of all six questions on decimals and significant figures, with full working explained step-by-step. The video breaks help students grasp the reasoning behind every step. Students are strongly encouraged to watch it to reinforce and deepen their understanding of the topic.