Answer:
Check the values in the combination with respect to the pascal's triangle. Use the value of n to determine the row, and the value of r to determine the exact number on the row.
Explanation:
For example, 5nCr2
Cr = combination
n= 5
n = 5th row
r= 2
r= the 2nd number on the fifth row after 1. When we count we don't include 1.
Using pascals triangle,
5nCr2 = 10
A sample of pascal's triangle has been attached to the solution.
Pascal's triangle involves the addition of numbers above to get the values below. The first number in the triangle is one. The next row, one is written twice forming a triangle. Let there be space between each number in the row.
1st row: 1
= 0 1 0
2nd row: 0+1 1+0 = 1 1
= 0 1 1 0
3rd row: 0+1 1+1 1+0 = 1 2 1
= 0 1 2 1 0
4th row: 0+1 1+2 2+1 1+0 = 1 3 3 1
The other rows follow same process.