Question

71. The total number of seven digit numbers the sum of whose
digits is even, is
​

Answer 1

Answer:

42+35=77

Step-by-step explanation:

For a seven Digit number using only 1,2,3 there are only two possible cases:

First case: 1 ,1,1,1,1,2,3

Now total possible arrangement of these no. can be given by-

Fact.( no. of digits ) / product of fact. (Individual repetition of numbers )

Which is = 7!/5!=42.

Division of 5! is Because of repetition of one five times.

Second Case : 1,1,1,1,2,2,2

Total arrangement of these no.

= 7! / ( 4! × 3! ) = 35.

4! is because of repetition of one four times and 3! Because of repetition of 2 three times.

So total no. are 42+ 35 = 77.

hope it helps!!!!!!!