Mental Subtraction Strategies Maths Grade 3 | Orchids
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Mental Maths

Mental Subtraction Strategies

  • Mental math is a skill that helps students to do math in their heads without using paper and pencil.
  • Mental Math is useful in school and everyday life.
  • It also helps to do calculations faster.

In subtraction,

  • The larger number is called the minuend.
  • The smaller number is called the subtrahend.
  • The resultant number is called the difference.
G3_1_Mental subtraction_Trickes

Method 1:(Add, and subtract)

  • Express the subtrahend as the difference of the nearest hundred in a one/two-digit number.
  • Then do the subtraction while adding the one/two-digit number with the minuend

Example:

G3_2_Mental subtraction_Example

Answer:

Now, 189 = 200 – 11

So, 278 – 200 + 11 = 78 + 11 = 89

G3_3_Mental subtraction_Answer

Method 2:(Split the Problems)

  • The basic idea is to split the minuend and subtrahend into two or more numbers which are easier to work with.
  • While splitting we will obviously take one number which is nearest to the hundred.

Example:

G3_4_Mental subtraction_Example

Answer:

  1. 568 = (500 + 68)
  2. 329 = (300 + 29)

    Now, 500 – 300 = 200

    68 – 29 = 39

    So, 200 + 39 = 239

    Hence, 568 – 329 = 239

    G3_5_Mental subtraction_Answer
  3. G3_6_Mental subtraction_Answer

Method 3:(Nikhilam rule)

  • Nikhilam rule says that “All from 9 and the last from 10.”
  • That means all digits should be subtracted from 9 and the last digit should be subtracted from 10.
  • After the subtraction, the difference should be added to the minuend.
  • Deleting the left first digit of the sum of the minuend and the result, we get the final result of the subtraction.

Example:

G3_7_Mental subtraction_Example

Answer:

  1. We need to subtract 123 from 9910 like the following way
  2. G3_8_Mental subtraction_Answer
  3. 897 – 250 =
  4. We need to subtract 250 from 9100 like the below way

    G3_9_Mental subtraction_Answer
G3_10_Mental subtraction_Did you know
G3_11_Mental subtraction_Mindmap
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