Divide to see how many laps he can swim in one minute, then multiply that by 3 1/2 to see how many laps he can swim in 3 1/2 minutes.
[tex]\sf\dfrac{1}{3}\div\dfrac{1}{6}[/tex]
You can multiply by the reciprocal.
[tex]\sf\dfrac{1}{3}\times\dfrac{6}{1}[/tex]
[tex]\sf\dfrac{6}{3}[/tex]
[tex]\sf 2[/tex]
