CONFIDENTIAL 1

Good Afternoon!

Today we will be learning about Adding and subtracting 2 decimal places

Let’s warm up :

Round to the nearest whole number:

1) 32.78

2) 4.32

Round to the nearest tenths:

3) 22.67

4) 7.885

Round to the nearest thousandths:

5) 8.4568

CONFIDENTIAL 2

Let’s review what we did in the last session.

Estimating, or being able to guess and come close to a correct answer, is an important part of mathematics and a very handy tool for

everyday life.

Rounding off is a kind of estimating.

We can round a decimal number with the help of a number line.

0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

3.4Round 3.4 to the nearest whole number.

The number 3.4 is closer to 3 than it is to 4.

So, the rounded value of 3.4 is 3.

Review

CONFIDENTIAL 3

We can round a decimal number using place value

3) If that digit is greater than or equal to five, add one to the rounding digit and drop all digits to the right of it.

To round off decimals:

1) Find the place value you want (the "rounding digit") and look at the digit just to the right of it.

2) If that digit is less than 5, do not change the rounding digit but drop all digits to the right of it.

Review

CONFIDENTIAL 4

Round 12.67 to the nearest tenth.

Look at the digit in the place to the right of where you want to round.

STEP 1:

12.67

STEP 2:

If it is less than 5 round down.If it is 5 or greater than 5, round up.

12.7

Round up to 12.7.

Hence, the rounded value of 12.67 to the nearest tenth is 12.7.

Review

CONFIDENTIAL 5

Review

To round 75.9876 to the nearest hundredths.

1) Find the rounding digit first.

2) This is the "8".We are trying to get rid of the all the digits to the right of the 8, but the result should be as accurate as possible.

3) Now look one digit to the right, at the digit in the thousandths place which is “7".

4) See that 7 is more than 5, Add one to the rounding digit and change all the rest of the digits to the right of it to zero. so the number "8" is incremented to “9”.

75.9876

75.9876

75.99

Hence, the rounded value of 75.9876 to the nearest hundredths is 75.99

CONFIDENTIAL 6

Let’s get started.Adding 2 decimal places

First let us know few key words before we start.

ADDEND: It is the number to be added.In 4.6 + 1.3 = 5.9,

4.6 and 1.3 are addends.

COMPENSATION: When adding, add a number to one addend and subtract the same number from the other addend to find the

sum. $2.30 + $3.50

- $0.30 + $0.30

= $2.00 + $3.80

= $5.80Add a

number

.Subtract

the same

number.

CONFIDENTIAL 7

Find 1.25 + 1.12.

We will add the decimal numbers with the help of 10 by 10 grids.

STEP 1:

The grids

display 1.25

The grids

display 1.12

Draw the grids displaying 1.25 + 1.12

CONFIDENTIAL 8

STEP 2: Put 1.25 and 1.12 together. The pink square shows 1.25 and blue square

shows 1.12.

STEP 3:Count the total number of shaded squares.100 + 100 + 37 = 237.

100 squares = 1 37 squares = 0.37

Therefore, the total number of shaded squares is = 2.37.

CONFIDENTIAL 9

We can add the decimal numbers on paperFind 12.45 + 21.

68.

STEP 1:

STEP 2:

12.45+ 21. 68 Line up the

decimal points.

12.45+ 21. 68

Add each place. Regroup if needed.Write the decimal point in the sum.

1 1

34.13

Carry

The sum is 34.13

CONFIDENTIAL 10

We will now learn to estimate the sum of decimal numbers

We know that estimate is an answer that is close to the exact answer.

Estimate 12.45 + 21.68.We will use rounding to find the estimated value.

STEP 1:

Rounding each addend to the nearest whole number.

12.45

rounds

to 12.

21.68 rounds to 22.

CONFIDENTIAL 11

STEP 2:

Add the estimated values of the addends.

12+ 22

34

Hence the estimated value of 12.45 + 21. 68 is 34.

Now your turn:

1) Find 36.26 + 16.67

2) Estimate 36.26 + 16.67

CONFIDENTIAL 12

Subtracting 2 decimal placesFirst let us know few key words before we start.

MINUEND: It is the number from which another number is to be subtracted.

DIFFERENCE: It is the answer to a subtraction problem.

SUBTRAHEND: It is the number to be subtracted from the Minuend.

7 – 3 = 4MinuendDifference

Subtrahend

CONFIDENTIAL 13

We will subtract the decimal numbers with the help of 10 by 10 grids.

Find 1.25 - 1.12

STEP 1:

Draw the grids displaying 1.25 - 1.12.Color 1 grid completely. Color 25 squares of the second grid.

The grids

display 1.25

CONFIDENTIAL 14

STEP 2:

Model 1.25 - 1.12 by crossing out all of the first grid and 12 colored squares on the second grid.

Count the number of shaded squares that are left.Here 13 squares are left.

Hence, the difference is 0.13.

CONFIDENTIAL 15

We can subtract the decimal numbers on paperFind 17.55 - 11. 18.

STEP 1:

STEP 2:

17.55- 11. 18 Line up the

decimal points.

Subtract each place. Regroup if needed.

Write the decimal point.4 15

6.37

Carry

The difference is 6.37

17.55- 11. 18

CONFIDENTIAL 16

STEP 3:

You can use the inverse relationship between addition and subtraction to check. + 6.37

17.55

11. 181

Find 21.32 - 7. 85.

CONFIDENTIAL 17

We will now learn to estimate the difference of decimal numbers

STEP 1:Rounding each addend to the nearest whole number.

17.55

rounds

to 18.

11.18 rounds to 11.

Estimate 17.55 - 11. 18.

STEP 2:

Subtract the estimated values of the Subtrahend from minuend.18

- 117

Hence the estimated value of 17.55 - 11. 18 is 7.

Estimate 21.32 - 7. 85.

CONFIDENTIAL 18

BREAK

CONFIDENTIAL 19

GAME

Click on the link below for some exciting puzzle

http://www.thekidzpage.com/onlinejigsawpuzzles/kids-jigsaw-puzzles/12-piece-jigsaw/03-27-07-donkey.html

Title: PUZZLEFormat: WebEx Web BrowserDouble-click to edit

CONFIDENTIAL 20

Assignments

Find the value of the following:

1) 3. 11 + 0.36

2) 44.92 + 21. 37 4) 44.92 - 21. 37

3) 3. 11 - 0.36

CONFIDENTIAL 21

Estimate the value of the following:

5) 3. 69 + 3.36

6) 5.92 + 7. 37 8) 11.32 - 4. 79

7) 7. 27 - 2.87

CONFIDENTIAL 22

9) Nancy bought a pencil for $1.24 and an eraser for $0.70. What is the total amount that she had to pay?

10) Ben bought a bag for $5.70 and a book for $4.25. By what amount the price of bag is more than the book ?

CONFIDENTIAL 23

Let’s Review what we did today

ADDEND: It is the number to be added.In 4.6 + 1.3 = 5.9,

4.6 and 1.3 are addends.

MINUEND: It is the number from which another number is to be subtracted.

DIFFERENCE: It is the answer to a subtraction problem.

SUBTRAHEND: It is the number to be subtracted from the Minuend.

7 – 3 = 4MinuendDifference

Subtrahend

CONFIDENTIAL 24

Find 12.45 + 21. 68.

STEP 1:

STEP 2:

12.45+ 21. 68 Line up the

decimal points.

12.45+ 21. 68

Add each place. Regroup if needed.Write the decimal point in the sum.

1 1

34.13

Carry

The sum is 34.13

Review

CONFIDENTIAL 25

Review

Find 17.55 - 11. 18.

STEP 1:

STEP 2:

17.55- 11. 18 Line up the

decimal points.

Subtract each place. Regroup if needed.

Write the decimal point.4 15

6.37

Carry

The difference is 6.37

17.55- 11. 18

CONFIDENTIAL 26

STEP 3:

You can use the inverse relationship between addition and subtraction to check. + 6.37

17.55

11. 181

Review

CONFIDENTIAL 27

STEP 1:Rounding each addend to the nearest whole number.

17.55

rounds

to 18.

11.18 rounds to 11.

Estimate 17.55 - 11. 18.

STEP 2:

Subtract the estimated values of the Subtrahend from minuend.18

- 117

Hence the estimated value of 17.55 - 11. 18 is 7.

Estimate 21.32 - 7. 85.

Review

CONFIDENTIAL 28

You have done a nice job.See you in the next session.