- Mental maths is defined as the ability to solve the arithmetic calculation mentally using the tricks.
- It takes less time to solve the problem.
- It increases the problem-solving ability in children.
- Regular practice of mental sums improves the child sense in numbers.

**Multiplication Tricks**

Multiplication of a whole number with the multiples of 10:

- Multiply the non-zero part of both the factors.
- Count the number of zeros in each of the factor.
- Add the same number of zeros in the product.

**Example 1:**

**Multiply 2100 by 400.**

**Solution:**

**Step 1: **Multiply 21 by 4

21 × 4 = 84**Step 2: **Total number of zeros in each of the factor = 4.**Step 3**: Add 4 zeros in the product 84.

840000

Therefore, 21 × 4 = 8,40,000.

**Example 2**:

**Multiply 100 by 1000.**

**Solution:**

**Step 1: **Multiply 1 by 1

1 × 1 = 1**Step 2: **Total number of zeros in each of the factor = 5.**Step 3: **Add 5 zeros in the product 1.

100000

Therefore, 100 × 1000 = 1,00,000.

**Multiplication of two digits number by a two digits number:**

**Step 1: **Multiply the unit digit of both the numbers.**Step 2: **Multiply the unit digit of multiplier by the ten digit of multiplicand and the ten digits of multiplier by the unit digit of multiplicand. Add them together.**Step 3: **Multiply the ten digits of both the number.

**Example:**

**Multiply 57 by 62.**

**Solution:**

Multiplication of two digits number by a two digits number when the ten digits are same and the sum of unit digit is 10:

**Step 1: **Multiply both the unit digits.**Step 2: **Multiply the ten digits by the succeeding digit.**Step 3: **Combine both the results.

**Example:**

**Multiply 27 by 23.**

**Solution:**

The sum of unit digit is 10 = (7 + 3).

Multiply 3 by 7 = 3 × 7 = 21

The digit in tens place is 2. The successor of 2 is 3.

Multiply 2 by 3 = 2 × 3 = 6.

The solution is 621.

**Multiplication of three digits number by a two digits number:**

**Example:**

**Multiply 157 by 23.**

**Solution:**

**Multiplication of three digits number by a three digits number:**

**Example:**

**Multiply 517 by 216.**

**Solution:**

Therefore, 517 × 216 = 1,11,672.

Multiplication of three digits number by a three digits number when the ten digits and hundred digits are same and the sum of unit digit is 10:

**Step 1: **Multiply both the unit digits.**Step 2: **Multiply the ten and the hundred digits by the succeeding digit.**Step 3: **Combine both the results.

**Example**:

**Multiply 277 by 273.**

**Solution:**

The sum of unit digit is 10 = (7 + 3).

Multiply 3 by 7 = 3 × 7 = 21

The digit in tenths and the hundreds place is 27. The successor of 27 is 28.

Multiply 27 by 28 = 27 × 28 = 756.

The solution is 75,621.

**Multiplication Tricks by Numbers**

**Rule for Multiplying by 9:**

- Multiply the number by 10.
- Subtract the number from product.

**Example 1:**

**Multiply 45 by 9**

**Solution:**

**Step 1: **Multiply 45 by 10.

45 × 10 = 450

**Step 2: **Subtract 45 from 450.

450 – 9 = 405

**Rule for Multiplying two digits number by 11:**

**Write the sum of the digits of the number in between the digits.**

**Example 1:**

Multiply 27 by 11

**Solution:**

**Rule for Multiplying three digits number by 11:**

**Example 2:**

Multiply 157 by 11.

**Solution:**

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