How can you use ratios to convert units of measurement

So exg

feet to inches or vice verca

so 12in=1ft

so

3 ft to in

conversion factor 12in/1ft

multiply 3 with 12in/1ft

ft units cancel

3 times 12=36=answer

convert 48 in to feet

1 ft=12 in

conversion factor 1ft=12in

multiply 48in with 1ft/12in

in cancel

48/12=4 ft