1.) Perimeter of rectangle with base B and Height H.
Perimeter =Â 2*(Base + Height)
Â
        = 2*(B + H)
2.) Nth odd number.
Odd number sequence = 1, 3, 5, 7, 9, 11, ........
                               (2n + 1)
zeroth, 0th, odd number = 1Â Â Â Â Â Â Â Â Â Â 2*0 + 1 = 1 Â Â
1st odd number = 3Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 2*1 + 1 = 3
2nd odd number = 5Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 2*2 + 1 = 5
3rd odd number = 7Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 2*3 + 1 = 7
4th odd number = 9Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â 2*4 + 1 = 9
And so on.  So the nth odd number starting from 0 is = 2n + 1.
         Â
3.) Area of triangle with Base B and Height H
   Area = (1/2)*B*H = (1/2)BH