what is the surface area of a triangular pyramid with a width of 30 a length of 30 and a height of 52

The word BALLOON has 7 characters, but only 5 letters (2 of them are repeated, L and O). The 5 letters used in the word are: B,A, L,O and N. In order to find the number of possible ways in which the letters can be arranged we need to note that:- there are 5 letters- two of them are used two times .To arrange 5 letters there are 5!=5*4*3*2*1=72 possibilities.To arrange the two O and A there are: 2!*2!=2*1*2*1=4So, there are 72/4=18 possible ways to arrange the letters in the word balloon.