Answer:
5 more men
Step-by-step explanation:
10 men do a job in 6 hours.
To do the job in 2 hours, 1/3 of the time, you need 3 times as many men.
30 men do a job in 2 hours.
To do the job in twice the time, 4 hours, you need half the men.
15 men do a job in 4 hours.
15 men - 10 men = 5 men
You need 5 more men.
