Transcript My Math Chapter 2

Multiply Whole Numbers
Lesson 1 – Prime Factorization
• Prime factorization is breaking down a composite
number into its prime factors.
• To find the prime factorization of a number, use a
factor tree.
Example:
18
↓ ↓
6 x 3
↓ ↓ ↓
3x2x 3
The prime factorization of 18 is 2 x 3 x 3 ( 2 x 3²).
Lesson 3 – Powers and Exponents
 3⁴
3 is the base
4 is the exponent
 The base is the number that is being
multiplied .
 The exponent tells you how many times you
multiply the base.
 Example:
3⁴=3x3x3x3
↓
↓
9 x 9 = 81
Lesson 4 – Multiplication Patterns
 With powers of 10 and other large numbers, you can use mental math to
solve.
 Example:
450 x 10³
↓
450 x 1,000
(the exponent tells you how
many zeros to add)
1. Multiply the numbers that are not zeros .
450 x 1,000
45 x 1 = 45
2. Count the number of zeros in the product. Put that many zeros in your
answer.
450 x 1,000
↓
↓
1 zero + 3 zeros = 4 zeros in answer
450 x 1,000 = 450,000
Lesson 5 – Problem-Solving Strategy: Make a Table
Janice is training for a marathon. She begins by running 2
miles the first week. Each week she runs double the
amount of miles. How many miles will she run during
week 4?
Double = x 2
Week
Miles
1
2
starting # x 2
2
3
4
4
8
16
x2
x2
Janice will run 16 miles during week 4.
Lesson 7 – The Distributive Property
You can use the Distributive Property to break numbers
into smaller ones that you can easily multiply.
Example:
8 x 12
↓↓
10 2
Break the digit down into tens and ones
Multiply and add the sums.
(8 x 10) + (8 x 2)
80 + 16 = 96
Lesson 8 – Estimate Products
1. Round numbers all the way to the left. Use the rules
for rounding .
92 → 90
x 12 → x 10
0 1 2 3 4 - round down
5 6 7 8 9 – round up
2. Multiply the non-zero numbers. Count the zeros.
90
x 10
900
9x1=9
1 zero + 1 zero = 2 zeros
Lesson 9 – Multiply by One-Digit Numbers
1. Multiply the ones.
873
x 2
6
2. Multiply the tens. Bring the digit in the tens place over to the
next number.
1
873
x 2
46
3. Multiply the hundreds. Add the number you carried over.
1
873
x 2
1,746
Lesson 10 – Multiply by Two-Digit Numbers
1. Multiply the ones.
4
56
x 17
392
2. Erase any markings. Add a zero to the next row.
3. Multiply the tens.
56
x 17
392
+ 560
4. Add the columns.
952