What is the least common multiple of 20, 30, and 130 ?

$60$

$78$

$180$

$780$

$78{,}000$

Approach 1

We should check if each answer choice is a multiple of each.

$60$, $78$, and $180$ are not multiples of $130$.

$780$ is a multiple of all three since it is divisible by all three numbers.

Approach 2

$$ 20 = 10\cdot 2 $$ $$ 30 = 10 \cdot 3 $$ $$ 130 = 10\cdot 13 $$

Therefore, the least common multiple will have all the common factors:

$$ 10 \cdot 2\cdot 3\cdot 13 = \boxed{780}$$