Squaring any number mentally using the
Criss-cross or Rainbow method is actually very fast and interesting to
calculate.

__Squaring a 2-digit Number using CRISS-CROSS method__

Step-1: Square the
unit’s (right) digit. Write a partial answer and carry, if any. This gives the
right most figure of the answer.

Step-2: Multiply both
the digit of the number to be squared and then double (multiply by 2) the
product. Add the carry, if any. Write again a partial answer and carry, if any.

Step-3: Square the
ten’s (left) digit and add carry, if any. Write the complete result. This gives
the left figure(s) of the answer.

Let’s say you want to square

**58**.
First, square the one’s digit that is
8. Square of 8 is 64. Write 4 and carry 6.

Then, multiply the two digits of the
number which are 5 and 8. So, 5 times 8 is 40. Now, double this product:
40×2=80. Add carry 6 to get 86. Write 6 and carry 8.

Finally, square the ten’s digit that is
5. Square of 5 is 25. Add carry 8 to get 33.

So, our final answer is 3364.

**67**

^{2}=?
1. Square of 7 is 49.
Write down 9 and carry 4.

2. Then, 6 times 7 is
42. And, 42×2 = 84. Add carry 4 to get 88. Write 8 and carry 8.

3. Finally, square of
6 is 36. And 36 plus carry 8 is 44. Write down 44.

So, the final answer is 4489.

Square of 3 is 9. Write 9. -> 9

7 times 3 is 21. And, 21×2=42. Write 2
and carry 4. -> 29

Square of 7 is 49. And 49 plus carry 4
is 53. Write down 53. -> 5329

So,

**73**^{2}=5329__Squaring a 3-digit Number using CRISS-CROSS method__

Step-1: Square the
unit’s (right) digit. Write a partial answer and carry, if any. This gives the
right most figure of the answer.

Step-2: Multiply the
middle digit by the right digit of the number and then double (multiply by 2)
the product. Add the carry, if any. Write again the units digit of the answer
and carry, if any.

Step-3: Multiply the
left digit with the right digit of the number and double the product. Add this
to the square of the middle digit and then add the carry. Write the units digit
of the answer and carry, if any.

Step-4: Multiply the left
digit with the middle digit of the number and double the product. Add carry.
Write the units digit of the answer and carry, if any.

Step-5: Square the
left digit and add carry, if any. Write the complete result. This gives the
left figure(s) of the answer.

Example,

**789**^{2}=?**9**

^{2}= 81. Write 1 carry 8**à**

**1**

**(9×8) × 2 = 144 + carry 8 = 152. Write 2, carry 15**

**à**

**21**

**(9×7) × 2 + 8**

^{2}= 126 + 64 = 190 + carry 15 = 205, write 5, carry 20**à**

**521**

**(8×7) × 2 = 112+carry 20 = 132. Write 2, carry 13**

**à**

**2521**

**7**

^{2}= 49 + carry 13 = 62. Write 62**à**

**622521**

**So, our final answer is**

**622521.**

what can be answer of square of 425

ReplyDeletesquare of 425

ReplyDelete