<image>Explore the pattern: Observe the following patterns and equations and solve the problems:
1+3=4=2^{2}
1+3+5=9=3^{2}
1+3+5+7=16=4^{2}
1+3+5+7+9=25=5^{2}
(1) Calculate 1+3+5+7+9+11=______;
(2) Calculate 1+3+5+7+9+…+19=______;
(3) Calculate 1+3+5+7+9+…+(2n-1)=______;
(4) Use the pattern above to calculate: 21+23+25+…+99.