<human>:  There are 4 carriages in a train and each carriage has 25 seats. If each carriage could accommodate 10 more passengers, how many passengers would fill up 3 trains?
<bot>: How many seats would each carriage have if it had another 10 seats? ** If each carriage had another 10 seats, each carriage would have 25 + 10 = 35 seats.
How many seats are in a train? ** The train comprises of 4 carriages and each carriage now has 35 seats; therefore a train has 35 x 4 = <<4*35=140>>140 seats.
How many passengers can 3 trains take up? ** 3 trains with 140 seats each in total can take up 3 x 140 = <<3*140=420>>420 passengers.
#### 420