Question

7. How many different 7-letter combinations can be

Answer 1

Answer:  20160

Explanation:

There are 8 letters in the word "GEOMETRY".

Use the nPr permutation formula with n = 8 and r = 7 and you'll find that 8P7 = 40320.

Or you can compute it like this 8*7*6*5*4*3*2 = 40320

This would be the answer if we could tell the E's apart.

However, we cannot tell the E's apart, so we have to divide by 2 to correct for the double-counting.

There are 40320/2 = 20160 different seven letter combinations possible.