How to solve for time?

Question

It takes 3 people 2 hours to enter 200 orders into an inventory system. Assuming the same rate of data entry, how long will it take 4 people to enter 100 orders?

Answer 1

if you asked how long 3 could do 100, it would be 1 hour, half as much

but you asked for 4, and you at least know it's less than 1 hour.

so whatecer calculation you come up with it's wrong if it's not less than 1 hour

if 3 do 200 in 2, then 3 do 100 in 1

each does 33 1/3 per hour

if there's 4, each does 33 1/3 per hour

when does 33 1/3 per hour times how many hours equal 100?

33 1/3 x T = 100

T=3

divide by 4 to get 3/4 of an hour to do 100

in 3/4 of an hour, each does 33 1/3. 3/4 x 4 x 33 1/3 = 100