Afet tooth eruption in permanent teeth the apex is fully developed after 2-3 years

Well over 50% of maxillary 1st molars have two canals in the mesiobuccal root. Some authors cite the number as high as 90%.

There are usually 3 roots and 4 canals in a maxillary 1st molar.
The fourth canal, the mesiolingual canal, is also referred to as: the accessory mesiobuccal canal, mesiocentric, mesiopalatal canal or MB2. 
It is usually tough to find MB2 through clinical inspection and it is not obvious on a radiograph. A dentist should expect it is present before beginning a root canal on the first maxillary molar.

madibular first molar normally have 3 root canals

A permanent tooth erupting in the mouth of an 11 years old child is most likely mandibular second bicuspid

permanent maxillary First molar teeth normally has four root canals