Problem: Pascal's triangle is an array of positive integers (See figure), in which the first row is , the second row is two l's, each row begins and ends with , and the th number in any row when it is not , is the sum of the th and th numbers in the immediately preceding row. The quotient of the number of numbers in the first rows which are not l's and the number of 's is
Answer Choices:
A.
B.
C.
D.
E. None of these
Solution:
In the first rows, there are 's and other numbers. The quotient is .