The other runners even tried to take the race out at a faster pace, but it didn't work.
"It suited me so it was a great race," Farah said. "I had a (cramp) from about eight laps to go and I was kind of pushing my stomach in, but then the pace slowed down and I tried to forget about it and come through."
In other finals, Aleksandr Menkov of Russia won the men's long jump title, with four-time champion Dwight Phillips 11th. Olympic champion Tatyana Lysenko of Russia captured the hammer throw.
There are two days still to go at the world championships, and two women's relays remaining. Felix had been planning to run in both.
That's not going to happen.
"This is life, man. Things happen in life," Merritt said. "That is just the way things go. Nothing is always going to be perfect."
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