5th Grade

1
Unit 2

• 5th Grade

2
Unit Goals

• Write and solve open sentences for number stories
• Round numbers to designated places
• Make magnitude estimates
• Find the product of multi-digit whole numbers and
  decimals
• Identify the maximum, minimum, median, mode, and
  mean for a data set (see data landmarks power
  point for more information)

3
Write and solve open sentences for number stories

• An open sentence is a number sentence or equation
  that contains a variable

I had three fish and bought some more at the pet
store. After two died, I had eight fish left.
How many fish did I buy?
f fish bought
Define your variable (the quantity you dont know)
3 f 2 8 1 f 8 f 7
Describe what took place using math operations
Combine like terms
Solve for the variable
4
Write and solve open sentences for number stories

• It often helps to look for key words to help you
  decide what operations to use.

Try one!
5
Which open sentence describes the following
number story? Lucas was comparing prices on a
pair of mini-speakers. At one store, the pair of
speakers cost 19.95. At a second store, the
same speakers cost 24.70. At a third store,
they cost 18.50. If he buys the speakers at the
lowest price, how much will he save over the
highest price?
24.70 - 19.95 s S savings
24.70 19.95 s S savings
24.70 19.95 s S savings
24.70 x 19.95 s S savings
6
Correct!

• The correct open sentence is 24.70 - 19.95 s
  because the phrase save over the highest price
  is asking you to find the DIFFERENCE
  (subtraction) between the highest and lowest
  prices.

Lucas was comparing prices on a pair of
mini-speakers. At one store, the pair of
speakers cost 19.95. At a second store, the
same speakers cost 24.70. At a third store,
they cost 18.50. If he buys the speakers at the
lowest price, how much will he save over the
highest price?
Click here to return to the goals page
7
Keep Trying!

• The correct open sentence is 24.70 - 19.95 s
  because the phrase save over the highest price
  is asking you to find the DIFFERENCE
  (subtraction) between the highest and lowest
  prices.

Lucas was comparing prices on a pair of
mini-speakers. At one store, the pair of
speakers cost 19.95. At a second store, the
same speakers cost 24.70. At a third store,
they cost 18.50. If he buys the speakers at the
lowest price, how much will he save over the
highest price?
Click here to return to the goals page
8
Round numbers to designated places

• Remember place value!
• Underline the value to which you are rounding
• Circle the digit to its right- this is the number
  you will need to look at
• If the circled digit is 5 or more, change the
  underlined digit to the next highest number and
  make the rest of the digits to the right into
  zeros
• If the circled digit is 4 or less, leave the
  underlined digit alone and make the rest of the
  digits to the right into zeros

9
Round numbers to designated places
Click the chest to play Place Value Pirates!
Click us to play a rounding game!

• Round 1,342,365.1427 to the nearest thousand.

You are being asked to tell whether
1,342,365.1427 is closer to 1,342,000 or
1,343,000.

• Underline the thousands place.
• Circle the hundreds place.
• The hundreds place is less than 5
• Leave the 2 alone and change 3 and everything to
  the right of it into zeros

Try one on your own!
1,342,000.0000
10
Round numbers to designated places

• Round 234,567,890.0987 to the nearest million.

234,000,000
200,000,000
235,000,000
230,000,000
11
Correct!

• The correct answer is 235,000,000.

Round 234,567,890.0987 to the nearest million.
Millions
Is 234,567,890.0987 closer to 234 million or 235
million?
234,567,890.0987
5 or more, round up!
Click here to return to the goals page
235,000,000
12
Keep Trying!

• The correct answer is 235,000,000.

Round 234,567,890.0987 to the nearest million.
Millions
Is 234,567,890.0987 closer to 234 million or 235
million?
234,567,890.0987
5 or more, round up!
Click here to return to the goals page
235,000,000
13
Make magnitude estimates
38 x 42

• A magnitude estimate is a ballpark estimate of
  what your answer should be.
• Its very helpful to use magnitude estimates to
  determine if your answer is reasonable.

• Round the factors to the nearest multiple of 10
• 38 is close to 40
• 42 is close to 40

2. Find the product of the two rounded
factors 40 x 40 1600
3. The answer should be in the 1000s
38 x 42 1596
14
Make magnitude estimates

• Make a magnitude estimate for 339 x 38 s.

300 x 40 1,200 The answer should be in the
1,000s
300 x 40 12,000 The answer should be in the
10,000s
400 x 40 16,000 The answer should be in the
10,000s.
400 x 40 1,600 The answer should be in the
1,000s
15
Correct!

• The correct answer is 300 x 40 12,000 The
  answer should be in the 10,000s.

339 x 38
3 3 9 X 3 8 ________ 2 7 1 2 1 0
1 7 0 ________ 1 2, 8 8 2
Click here to return to the goals page
16
Keep Trying!

• The correct answer is 300 x 40 12,000 The
  answer should be in the 10,000s.

Be sure to round to the nearest multiple of 10-
the numbers highest place value!
3 3 9 X 3 8 ________ 2 7 1 2 1 0
1 7 0 ________ 1 2, 8 8 2
339 x 38
339 is closest to 300 38 is closest to 40 300 x
40 12,000
Click here to return to the goals page
17
Find the product of multi-digit whole numbers and
decimals

• When multiplying multi-digit numbers, remember to
  keep place value lined up!

Divide each number by .1
5
3
4
.
0
x
2
.
3
Multiply 5340 x 3
0
2
2
5
1
0
0
8
6
0
1
Multiply 5340 x 20
Multiply by .01
Add the products
.
0
2
0
2
2
1
18
Find the product of multi-digit whole numbers and
decimals

• You can also multiply this way

5
3
4
x
2
3
Multiply 20 x 500
0
1
0
0
0
6
Multiply 20 x 30
0
0
0
8
Multiply 20 x 4
5
1
0
0
Multiply 3 x 500
Multiply 3 x 30
9
0
1
2
Multiply 3 x 4
Add the products
2
8
2
2
1
19
Find the product of multi-digit whole numbers and
decimals

• A third way to multiply is

5
3
4
x
2
3
Multiply 20 x 500
0
1
0
0
0
6
Multiply 20 x 30
0
0
0
8
Multiply 20 x 4
5
1
0
0
Multiply 3 x 500
Multiply 3 x 30
9
0
1
2
Multiply 3 x 4
Add the products
8
2
2
1
2
20
The Lattice Method

• Click here for a demonstration of the lattice
  method of multiplication.
• Another demonstration page

21
Find the product of multi-digit whole numbers and
decimals

• Use a method of multiplication to solve the
  following open number sentence
• 43.25 x 36 N

N 125.7
N 1557
N 15570
N 1257
22
Correct!

• The correct answer is 43.25 x 36 1557.

43.25 x 36
4 3 . 2 5 X 3 6 . 0 0
___________ 2 5 9 5 0 0 0 1 2 9 7 5 0 0
0 ___________ 1 5 5 7. 0 0 0 0
Click here to return to the goals page
23
Keep Trying!

• The correct answer is 43.25 x 36 1557.

43.25 x 36
4 3 . 2 5 X 3 6 . 0 0
___________ 2 5 9 5 0 0 0 1 2 9 7 5 0 0
0 ___________ 1 5 5 7. 0 0 0 0
Click here to return to the goals page