ADD AND SUBTRACT INTEGERS

Example 1 :

Evaluate :

5 + 8

Solution :

Since both the given numbers are positive, we have to add them and the result is positive.

5 + 8 = 13

Example 2 :

Evaluate :

- 3 - 6

Solution :

Since both the given numbers are negative, we have to add them and the result is negative.

- 3 - 6 = -9

Example 3 :

Evaluate :

-3 + 5

Solution :

Since the given two numbers are having different signs, subtract the smaller from larger and take the sign of the larger number to the answer.

- 3 + 5 = 2

Example 4 :

Evaluate :

5 - 8

Solution :

Since the given two numbers are having different signs, subtract the smaller from larger and take the sign of the larger number to the answer.

5 - 8 = -3

Example 5 :

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 6 :

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 7 :

Add 7957, 6438 and 4539.

Solution :

7,957 + 6,438 + 4,539

Therefore,

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

Example 8 :

Add 18534, 5879 and 6261.

Solution :

18,534 + 5,879 + 6,261

Therefore,

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

Example 9 :

Subtract 5011 from 7412.

Solution :

7,412 - 5,011

Therefore,

7,412 - 5,011 = 2,401

Example 10 :

Subtract 8534 from 25986.

Solution :

25,986 - 8534

Therefore,

25,986 - 8,534 = 17,452

Example 11 :

Subtract 3907 from 4210.

Solution :

4,210 - 3,907

Therefore,

4,210 - 3,907 = 303

Example 12 :

Subtract 3847 from 5410.

Solution :

5,410 - 3,847

Therefore,

5,410 - 3,847 = 1,563

Example 13 :

Add 56051 and 232342.

Solution :

56,051 + 232,342

Therefore, 

56,051 + 232,342 = 288,393

Example 14 :

Add 725708 and 310562.

Solution :

725,708 + 310,562

Therefore,

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

Example 15 :

On Monday Sarah sold 54 cups of lemonade. On Tuesday she sold 71 cups of lemonade. How many more cups did she sell on Tuesday compared to Monday?

(a) 15     (b) 16    (c) 17      (d) 18

Solution :

Number of cups of lemonade sold on Monday = 54

Number of cups of lemonade sold on Tuesday = 71

On Tuesday more number of cups of lemonade sold on Monday.

= 71 - 54

= 17

So, there are 17 more lemonade cups sold.

Example 16 :

Neol baked 8 cupcakes for her daughter and her friends. The weight of each cupcake is 170 grams. The entire box including the cupcakes weighs 1 kg 750 grams. Find the weight of the box: 

(a) 360 grams     (b) 390 grams    (c) 420 grams

(d) 450 grams

Solution :

Number of cupcakes baked = 8

Weight of one cupcake = 17 grams

Weight of all 8 cupcakes = 170 x 8

= 1360 grams

Weight of 8 cupcakes + weight of box = 1 kg 750 grams

= 1750 grams

1360 + weight of box = 1750

weight of box = 1750 - 1360

= 390 grams

Example 17 :

Meh has $432 more than 7 times the money that Rebek has. If Rebek has $280, how much money does Meh have?

a) $4,984   b) $3,654    c) $2,392     d) $1,856

Solution :

Amount Rebek has = $280

Amount Meh has = 7(280) + 432

= 1960 + 432

= $2392

So, option c is correct.

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