## A.11 Sum-Average

1. Find summation of 3-digits numbers made using 1, 2, & 3 and 4-digits numbers using 1, 2, 3, 4.
2. Find summation of all possible numbers above 100,00, made using the digits 0, 2, 4, 6, 8.
3. Sum of all possible numbers using 1, 2, 3, 4, each just once.
4. Make the general formula to find sum of all possible numbers
5. Average of 9-digit numbers made using 5 five times and 4 four times.
6. Find sum of numbers greater than 10,000, using 1, 3, 5, 7, 9
7. Find sum of all possible numbers, using 1, 3, 5, 7, 9
1. 2!(1+2+3)(1+10+100) & 3!(1+2+3)1111
1. 4!(0+2+4+6+8)(1+10+100+1000+10000)-3!(2+4+6+8)(1+10+100+1000)
1. $$3! (1+2+3+4)(1111)+^3P_2 \times 10 \times 111+ ^3P_1 \times 10 \times 11 + 10$$
1. $$(n-1)! \times D \times \sum_{i=0}^n 10^i$$; (D = Sum of digits, n = no. of digits in the numbers made)
1. $$n=\frac{9!}{5!4!}, \bar X=\frac{}{n}$$
1. All 5-digit numbers: 4!(1+3+5+7+9)11111=6666600
1. 1, 2, 3, o4 4 digit numbers: 4!(1+3+5+7+9)11111+…