Find the LCM 16ab^3 , 5b^2a^2 , 20ac

$16 a b^{3}$ , $5 b^{2} a^{2}$ , $20 a c$

Step 1

Since $16 a b^{3}, 5 b^{2} a^{2}, 20 a c$ contains both numbers and variables, there are two steps to find the LCM. Find LCM for the numeric part $16, 5, 20$ then find LCM for the variable part $a^{1}, b^{3}, b^{2}, a^{2}, a^{1}, c^{1}$ .

Step 2

The LCM is the smallest positive number that all of the numbers divide into evenly.

1. List the prime factors of each number.

2. Multiply each factor the greatest number of times it occurs in either number.

Step 3

The prime factors for $16$ are $2 \cdot 2 \cdot 2 \cdot 2$ .

$16$ has factors of $2$ and $8$ .

$2 \cdot 8$

$8$ has factors of $2$ and $4$ .

$2 \cdot 2 \cdot 4$

$4$ has factors of $2$ and $2$ .

$2 \cdot 2 \cdot 2 \cdot 2$

Step 4

Since $5$ has no factors besides $1$ and $5$ .

$5$ is a prime number

Step 5

The prime factors for $20$ are $2 \cdot 2 \cdot 5$ .

$20$ has factors of $2$ and $10$ .

$2 \cdot 10$

$10$ has factors of $2$ and $5$ .

$2 \cdot 2 \cdot 5$

Step 6

The LCM of $16, 5, 20$ is the result of multiplying all prime factors the greatest number of times they occur in either number.

$2 \cdot 2 \cdot 2 \cdot 2 \cdot 5$

Step 7

Multiply $2 \cdot 2 \cdot 2 \cdot 2 \cdot 5$ .

Multiply $2$ by $2$ .

$4 \cdot 2 \cdot 2 \cdot 5$

Multiply $4$ by $2$ .

$8 \cdot 2 \cdot 5$

Multiply $8$ by $2$ .

$16 \cdot 5$

Multiply $16$ by $5$ .

$80$

Step 8

The factor for $a^{1}$ is $a$ itself.

$a^{1} = a$

$a$ occurs $1$ time.

Step 9

The factors for $b^{3}$ are $b \cdot b \cdot b$ , which is $b$ multiplied by each other $3$ times.

$b^{3} = b \cdot b \cdot b$

$b$ occurs $3$ times.

Step 10

The factors for $b^{2}$ are $b \cdot b$ , which is $b$ multiplied by each other $2$ times.

$b^{2} = b \cdot b$

$b$ occurs $2$ times.

Step 11

The factors for $a^{2}$ are $a \cdot a$ , which is $a$ multiplied by each other $2$ times.

$a^{2} = a \cdot a$

$a$ occurs $2$ times.

Step 12

The factor for $a^{1}$ is $a$ itself.

$a^{1} = a$

$a$ occurs $1$ time.

Step 13

The factor for $c^{1}$ is $c$ itself.

$c^{1} = c$

$c$ occurs $1$ time.

Step 14

The LCM of $a^{1}, b^{3}, b^{2}, a^{2}, a^{1}, c^{1}$ is the result of multiplying all prime factors the greatest number of times they occur in either term.

$a \cdot a \cdot b \cdot b \cdot b \cdot c$

Step 15

Simplify $a \cdot a \cdot b \cdot b \cdot b \cdot c$ .

Multiply $a$ by $a$ .

$a^{2} \cdot b \cdot b \cdot b \cdot c$

Multiply $b$ by $b$ by adding the exponents.

Move $b$ .

$a^{2} \cdot (b \cdot b) \cdot b \cdot c$

Multiply $b$ by $b$ .

$a^{2} \cdot b^{2} \cdot b \cdot c$

Multiply $b^{2}$ by $b$ by adding the exponents.

Move $b$ .

$a^{2} \cdot (b \cdot b^{2}) \cdot c$

Multiply $b$ by $b^{2}$ .

Raise $b$ to the power of $1$ .

$a^{2} \cdot (b^{1} b^{2}) \cdot c$

Use the power rule $a^{m} a^{n} = a^{m + n}$ to combine exponents.

$a^{2} \cdot b^{1 + 2} \cdot c$

Add $1$ and $2$ .

$a^{2} \cdot b^{3} \cdot c$

$a^{2} b^{3} c$

Step 16

The LCM for $16 a b^{3}, 5 b^{2} a^{2}, 20 a c$ is the numeric part $80$ multiplied by the variable part.

$80 a^{2} b^{3} c$

Find the LCM 16ab^3 , 5b^2a^2 , 20ac

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