How many 4-letter code can be formed using the first 10 letters of the English alphabet, if no letter can be repeated?

How many 5-digit telephone numbers can be constructed using the digits 0 to 9 if each number starts with 67 and no digit appears more than once?

. A coin is tossed 3 times and the outcomes are recorded. How many possible outcomes are there?

A coin is tossed 3 times and the outcomes are recorded. How many possible outcomes are there?

Given 5 flags of different colours, how many different signals can be generated if each signal requires the use of 2 flags, one below the other?

Evaluate (i) 8!

Is 4! + 3! = 7!?

Compute 8!/6!×2!

If 1/6!+1/7!=x/8! , find x.

Evaluate n!/(n - r)!

(i) n = 6, r = 2 (ii) n = 9, r = 5

How many 3-digit numbers can be formed by using the digits 1 to 9 if no digits is repeated?