Year 3 Exam  >  Year 3 Notes  >  Year 3 Mathematics  >  How to add and subtract in your head

How to add and subtract in your head | Year 3 Mathematics PDF Download

Rounding numbers

Rounding numbers can simplify addition by adjusting numbers to the nearest multiple of 10 or 100.
Here are some examples:

  • When adding 9 to a number:
    • Step 1: Add 10 to the number.
    • Step 2: Subtract 1 from the result to adjust back.
    • Example: 36 + 9 = 36 + 10 - 1 = 45
  • When adding 18 to a number:
    • Step 1: Add 20 to the number.
    • Step 2: Subtract 2 from the result to get the final sum.
    • Example: 48 + 18 = 48 + 20 - 2 = 66
  • When adding 97 to a number:
    • Step 1: Add 100 to the number.
    • Step 2: Subtract 3 to adjust and find the sum.
    • Example: 439 + 97 = 439 + 100 - 3 = 536
  • When adding 0.9 to a number:
    • Step 1: Add 1 to the number.
    • Step 2: Subtract 0.1 from the result to get the final sum.
    • Example: 3.7 + 0.9 = 3.7 + 1 - 0.1 = 4.6

Breaking Down Numbers

Breaking down numbers can be a useful strategy to mentally add or subtract numbers.
For instance, let's consider finding the difference between 38 and 63:

  • Start by counting from 38 to 40, keeping the difference of 2 in mind.
  • Next, count from 40 to 60, which is a difference of 20.
  • Finally, count from 60 to 63, which is a difference of 3.
  • Add these differences together: 2 + 20 + 3 = 25.

Question for How to add and subtract in your head
Try yourself:
What is the result of adding 68 to a number using the rounding method described in the text?
View Solution

The document How to add and subtract in your head | Year 3 Mathematics is a part of the Year 3 Course Year 3 Mathematics.
All you need of Year 3 at this link: Year 3
69 videos|67 docs|11 tests

Top Courses for Year 3

69 videos|67 docs|11 tests
Download as PDF
Explore Courses for Year 3 exam

Top Courses for Year 3

Signup for Free!
Signup to see your scores go up within 7 days! Learn & Practice with 1000+ FREE Notes, Videos & Tests.
10M+ students study on EduRev
Related Searches

How to add and subtract in your head | Year 3 Mathematics

,

shortcuts and tricks

,

How to add and subtract in your head | Year 3 Mathematics

,

mock tests for examination

,

Important questions

,

Previous Year Questions with Solutions

,

Objective type Questions

,

How to add and subtract in your head | Year 3 Mathematics

,

ppt

,

past year papers

,

Semester Notes

,

Sample Paper

,

video lectures

,

MCQs

,

Extra Questions

,

pdf

,

Viva Questions

,

Exam

,

practice quizzes

,

Free

,

Summary

,

study material

;