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Mental Addition & Subtraction by using Place value

a)Fast & Easy Addition

Doing addition & subtraction is not a difficult task, but by using conventional method it is difficult to do addition orally. Here we learn to add the number by adding their place value. By using place value one can easily add the numbers mentally.

First, we will solve by conventional method

Ex. i) 256 + 477

 

Step 1: In conventional method, first, we add from right hand side, 6+7 =13

3 retained as right most digit of the answer & 1 carry over to the left hand

Digit.

 

Step 2: Now we add, 5 +7 = 12+ 1 (Carry)= 13, Here 3 retained in answer & carryover 1 to the leftmost digit.

 

Step 3:  Now add 2 + 4 = 6 + 1 (Carry) = 7

Answer = 256

Fast addition

 

Now, if we try to add this number mentally then it’s not possible by conventional   method, for mental addition we must add them by their place value.

 

 256 + 477  is,

200 + 400 =600 (Add place value of first digit)

50 + 70 = 120 (Add place value of second digit)

6 + 7 = 13 (Add place value of third digit)

Now add the results, 600 + 120 + 13 = 733.

Answer, 256 + 477 = 733

 

OR

 

256 + 477

Take 256 & add 400 (Place value of first digit)

256 + 400 = 656

Now, add 70 (Place value of second digit)

656 + 70 =726

Now add 7 (Third digit place value)

726 + 7 =733

Answer, 256 + 477 = 733

 

Ex. ii) 4567 + 2543 + 7896

4000 + 2000 + 7000 =13000

500 + 500 + 800 = 1800

60 + 40 + 90 = 190

7 + 3 + 6 =16

Add the results,

13000 + 1800 + 190 + 16 =15006

Answer, 4567 + 2543 + 7896 = 15006

 

Ex. iii) 456 + 762

456 + 700 =1156

1156 + 60 =1216

1216 + 2 = 1218

Answer, 456 + 762 = 1218

 

Ex. iv) 7206 + 2366

7976 + 2000 = 9206

9206 + 300 = 9506

9406 + 60 = 9466

9466 + 6 =9472

Answer, 7206 + 2366 = 9472

 

b) Easy & Fast Subtraction:

Ex. v) 4288 – 3219

  First, we will solve by conventional method,

          

 

Step 1: we start to subtract number from RHS.

8-9, Here we need to barrow from left hand side digit

So, we borrow 1 from 7

Now, 18 -9 = 9

 

Step 2: Now we subtract 10th place number,

6 -1 = 5 (Here we subtract from 6, as we borrow 1 from 7)

 

Step 3: Now we subtract 100th place number

2-2 = 0

 

Step 4: Now we subtract our right most digit,

4 – 3 =1

 

So, our answer is, 1059

But by using conventional method it is not possible to subtract number mentally, so for mental subtraction we will use place value of the number.

 

Now we will solve by using place value,

4278 – 3219

4278 – 3000 =1278 (Subtract place value of 1st number from right)

1278- 200 = 1078 (Subtract place value of 2nd number)

1078- 10 = 1068 (Subtract place value of 3rd number)

1068 – 9 = 1059 (Subtract place value of 4th number)

So, Answer = 1059

By practicing we can do subtraction orally.

 

Ex. vi) 567 – 348

  567 – 300 =267

267 – 40 =227

227 – 8 = 219

Answer, 567 – 348 = 219

 

Ex. vii) 4356 -1478

4356 – 1000 =3356

3356 – 400 = 2956

2956 – 70 = 2886

 2886 – 8 = 2878

Answer, 4356 -1478 = 2878

 

Try This Orally:

i) 453 + 673  ii) 2351 + 5322  iii) 1546 + 243

iv) 345-267   v) 5672 – 4378   vi) 3412 – 2423

 

To study more find this links:

i) Multiplication tricks of vedic maths

ii) Easiest method to Divide the number by 9 

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