Mental Math

Mental Multiplication 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 multiplication,

• The number with which we multiply is called the multiplicand.
• The number which is multiplied by the multiplicand is called the multiplier
• The result of a multiplication is called the product.

Method 1:

• Multiply each number from left to right with the multiplier. Let us discuss with an example.

Example :

a) 42 × 7

Answer:

Method 2:

• Round off the multiplicand to the nearest ten
• Then do the multiplication
• After that, multiply the reduced or additional value of the rounded off number with the multiplier.
• Then subtract/add the product from the previous one. Let us discuss with examples.

Example :

a) 78 × 3

b) 44 × 6

Answer:

a) 78 × 3 = (80 – 2) × 3

b) 44 × 6 = (40 + 4) × 6

Method 3:

• Split the multiplier into factors.
• Multiply the numbers multiplicand with the first factor
• Then multiply the product of the previous multiplication with the second factor.
• Continue the same process with all the factors.

Let us discuss with examples.

Example :

a) 24 × 8

b) 25 × 44

Answer:

a)

So, 24 × 8 = 192

b)

So, 25 × 44 = 1100

Method 4:

• Break the multiplier as the sum/difference of the nearest ten/ hundred and a one-digit number.
• Multiply by each from right to left.
• Add the individuals to get the final answer.
• Let us discuss with examples.

Example :

a) 46 × 12

b) 23 × 18

Answer:

a) 46 × 12 = 46 × (10 + 2) =

So, 46 × 12 = 552

b) 23 × 18 = 23 × (20 - 2)

So, 23 × 18 = 414

Method 5:

• Round up the multiplier to the nearest hundred.
• Multiply the rounded-up value and the amount rounded up from left to right.
• Subtract the products

Example :

27 × 96

Answer:

27 × 96 = 27 × (100 – 4)

Method 6:

• Express both the multiplier and multiplicand as the sum of the nearest ten and a one/ two digit.
• Now multiply and add.

Example :

35 × 22

Answer:

35 = (30 + 5)

22 = (20 + 2)

Hence, 35 × 22 = 770