Finding the LCD (Least Common Denominator)

[cmrcheer]

I've been stuck on this math problem for about an hour and I just cannot get it.

Heres the math problem: Find the LCD of the following list of fractions 1/3, 17/42, 50/91

I factored each number out so:
3=3
42=7 * 6 = 7 * 2 * 3
91= 91 since its a prime number.

This is the part where I get stuck.. so would it be 7 * 2 * 3 = 42?
If I confused you at all, please let me know and I'll try to explain it better. Thanks for your time!

 

[cmrcheer]

I've been stuck on this math problem for about an hour and I just cannot get it.

Heres the math problem: Find the LCD of the following list of fractions 1/3, 17/42, 50/91

I factored each number out so:
3=3
42=7 * 6 = 7 * 2 * 3
91= 91 since its a prime number.

This is the part where I get stuck.. so would it be 7 * 2 * 3 = 42?
If I confused you at all, please let me know and I'll try to explain it better. Thanks for your time!

Oops, forgot the 91.. so 7 * 2 * 3 * 91 = 3822? This seems too big of a number to be the LCD, which confuses me.

 

[soroban]

Hello, cmrcheer!

You missed a factoring . . . a sneaky one!

\(\displaystyle \text{Find the }LCD\text{ of: }\:\dfrac{1}{3}\;\;\dfrac{17}{42}\;\;\dfrac{50}{91}\)

. . \(\displaystyle \begin{array}{cccc}3 &=& 3 \\ 42 &=& 2\cdot3\cdot7 \\ 91 &=& 7\cdot13 & \leftarrow\end{array}\)


\(\displaystyle LCD \:=\:2\cdot3\cdot7\cdot13 \:=\:546 \)