Let 88" title="Click to view the MathML source">m,n≥3, (m−1)(n−1)+2≤p≤mn, and u=mn−p. The set Ru×n×m of all real tensors with size u×n×m is one to one corresponding to the set of bilinear maps Rm×Rn→Ru. We show that 99ad93a6633c8461ad5f79" title="Click to view the MathML source">Rm×n×p has plural typical ranks p and p+1 if and only if there exists a nonsingular bilinear map Rm×Rn→Ru. We show that there is a dense open subset O of Ru×n×m such that for any Y∈O, the ideal of maximal minors of a matrix defined by Y in a certain way is a prime ideal and the real radical of that is the irrelevant maximal ideal if that is not a real prime ideal. Further, we show that there is a dense open subset e9e74c8a89fe4554e20028030ccd0b9b" title="Click to view the MathML source">T of 884ca4e48167" title="Click to view the MathML source">Rn×p×m and continuous surjective open maps e9a5b87345635826f14262b" title="Click to view the MathML source">ν:O→Ru×p and σ:T→Ru×p, where Ru×p is the set of bedf99013c" title="Click to view the MathML source">u×p matrices with entries in 990d9f7614754697d5bdc24a1b766c83" title="Click to view the MathML source">R, such that if ν(Y)=σ(T), then 9980604628dcb00ee46b2"> if and only if the ideal of maximal minors of the matrix defined by Y is a real prime ideal.