ADDING AND SUBTRACTING WHOLE NUMBERS

Example 1 :

Add 2489, 9605 and 3814.

Solution :

2,489 + 9,605 + 3,814

Step 1 :

Add the digits in ones place.

9 + 5 + 4 = 18

Write 8 as a result in ones place and carry 1 to tens place.

Step 2 :

Add the digits in tens place.

1 + 8 + 0 + 1 = 10

Write 8 as a result in tens place and carry 1 to hundreds place.

Step 3 :

Add the digits in hundreds place.

1 + 4 + 6 + 8 = 19

Write 9 as a result in hundreds place and carry 1 to thousands place.

Step 3 :

Add the digits in thousands place.

1 + 2 + 9 + 3 = 15

Therefore,

2,489 + 9,605 + 3,814 = 15,908

Example 2 :

Subtract 2341 from 8623.

Solution :

8623 - 2341

Step 1 :

Subtract the digits in ones place.

3 - 1 = 2

Write 2 as a result in ones place.

Step 2 :

Subtract the digits in tens place.

2 - 4 = ?

Since 2 is less than 4, you can't subtract 4 from 2.

So, borrow 1 from the digit 6 in hundreds place of 8623 and make 2 in tens place as 12. Then, subtract 4 from 12.

12 - 4 = 8

Step 3 :

Subtract the digits in hundreds place.

5 - 3 = 2

Write 2 as a result in hundreds place.

Step 4 :

Subtract the digits in thousands place.

8 - 2 = 6

Write 2 as a result in thousands place.

Therefore,

8,623 - 2,341 = 6,282

Example 3 :

Add 7957, 6438 and 4539.

Solution :

7,957 + 6,438 + 4,539

Therefore,

7,957 + 6,438 + 4,539 = 18,934

Example 4 :

Add 18534, 5879 and 6261.

Solution :

18,534 + 5,879 + 6,261

Therefore,

18,534 + 5,879 + 6,261 = 30,674

Example 5 :

Subtract 5011 from 7412.

Solution :

7,412 - 5,011

Therefore,

7,412 - 5,011 = 2,401

Example 6 :

Subtract 8534 from 25986.

Solution :

25,986 - 8534

Therefore,

25,986 - 8,534 = 17,452

Example 7 :

Subtract 3907 from 4210.

Solution :

4,210 - 3,907

Therefore,

4,210 - 3,907 = 303

Example 8 :

Subtract 3847 from 5410.

Solution :

5,410 - 3,847

Therefore,

5,410 - 3,847 = 1,563

Example 9 :

Add 56051 and 232342.

Solution :

56,051 + 232,342

Therefore, 

56,051 + 232,342 = 288,393

Example 10 :

Add 725708 and 310562.

Solution :

725,708 + 310,562

Therefore,

725,708 + 310,562 = 1,036,270

Example 11 :

If P = 53527, Q = 32635, P + Q - R = 72573, then what is the value of R

a)  13899    b)  13589     c)  12869     d)  13789

Solution :

P = 53527, Q = 32635, P + Q - R = 72573

P + Q = 53527 + 32635

= 86162

86162 - R = 72573

R = 86162 - 72573

R = 13589

So, option b is correct

Example 12 :

Add 464, 723, 824 then

i) If the sum is an even number, then increase the number by 45535

ii) If the sum is an odd number, then decrese the number by 2010

a)  2011    b)  1     c)  0     d)  1999

Solution :

First we add, 464, 723 and 824

= 464 + 723 + 824

= 2011

The sum is odd. Then decreases by 2010

= 2011 - 2010

= 1

So, option b is correct.

Example 13 :

A is a natural number which is three times of 2105. subtract 576 from 874 and add the result to A. What is the answer ?

a)  4413    b)  5513     c)  6613     d)  7613

Solution :

Subtracting 874 and 576, we get

874 - 576 = 298

A = 3(2105)

= 6315

Adding the difference with 6315,

= 6315 + 298

= 6613

So, the answer is option c.

Example 14 :

The population of a town is 198568. Out of them 75312 are men and 55678 are women. Find the number of children in the town.

a)  55578    b)  67578     c)  65578     d)  45578

Solution :

Total population = 198568

Number of men = 75312

Number of women = 55678

Number of men + number of women + number of children

= 198568

75312 + 55678 + number of children = 198568

130990 + number of children = 198568

number of children = 198568 - 130990

= 67578

So, number of children is 67578. Option b is correct.

Example 15 :

Identify the number that should fill the blank in the following.

9056 + 2058 = 2058 + ?

a)  0   b)  9056     c)  2058     d)  1114

Solution :

Given that,

9056 + 2058 = 2058 + ?

Using commutative property, by changing the order the result will not be changed. Then, the answer is 9056, option b.

Example 16 :

B is twice of A, C is thrice of B and D is four times of C. If D is equal to 5424, then find the value of A + B + C + D 

a)  7285   b)  7458    c)  4175     d)  3676

Solution :

B = 2A

C = 3B

D = 4C

D = 5424

To get C, we divide D by 4. Then 5424/4 ==> 1356

To get B, we divide C by 3. Then 1356/3 ==> 452

To get A, we divide B by 2. Then 452/2 ==> 226

A + B + C + D = 226 + 452 + 1356 + 5242

= 7458

So, option b is correct.

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