The least common multiple of $3$, $4$ and $5$ is $60$. We know that $60\div7=8\ldots\ldots4$, then the remainder tells us that it will be on Thursday. 
Barb likes to help her father with housework. She dusts every $3$ days, sweeps every $4$ days, and cooks dinner every $5$ days. If she does all $3$ chores on one Sunday, she next does all $3$ on the same day on a ． 

1: Wednesday 
2: Thursday 
3: Friday 
4: Saturday 