In one hour, they travel 8 kilometers. They then have 4 kilometers left. 4 is half. of 8, so I would possibly take half the time it would to travel 8, making it 30 minutes for the other 4 kilometers.
To find the circumference of a circle you need to take the diameter times Pi. So if you need to find the diameter from the circumference, simply divide the circumference by 3.14 which is Pi
Gemma was hiking for 2 1/2 a hour for 3 hours so u have to multiply 2.5 by 3 and that gonna equal 7.5 so u leave that alone and come back to it later so u get 11 3/8 minus 7.5 and it gonna equal 3 7/8 and I hope that helped you