The 10 people shovel 10,000 pounds per 10 days, or 10,000/10=<<10000/10=1000>>1000 pounds per day per 10 people.
And 1000 pounds per day per 10 people is 1000/10=<<1000/10=100>>100 pounds per day per person.
Half of ten people is 10/2=<<10/2=5>>5 people.
At 100 pounds per day per person, 5 people can shovel 5*100=<<5*100=500>>500 pounds per day.
Therefore, for 5 people to shovel 40,000 pounds, it will take 40,000/500=<<40000/500=80>>80 days.
#### 80