find how many 5 digit number can be formed by using 1,2,3,4,5,6,7,8,9 and also find its sum
no useless answer
Answers
Answer:
i know
Step-by-step explanation:
Correct option is
A
3
If 5 is at the unit's place, the remaining digits 1,2,3 and 4 can be arranged among themselves in 4! ways. Hence, there are exactly 4! five-digit numbers using the given digits.
Similarly, there are exactly 4! five-digit numbers using the given digits. Similarly for other digits.
Hence the total sum of digits at unit's place for all numbers possible is 4!(5+4+3+2+1)
Similarly, the total sum of digits at ten's place for all numbers possible is 10×4!(5+4+3+2+1)
Similarly, for hundred's, thousand's and ten thousand's place the sum are 10
2
×4!(5+4+3+2+1),10
3
×4!(5+4+3+2+1),10
4
×4!(5+4+3+2+1) respectively.
Hence, the required sum
=(4)!(1+2+3+4+5)(1+10+10
2
+10
3
+10
4
)
=24×15×(
10−1
10
5
−1
)
=24×15×11111
=3999960
The first digit is 3.
Answer:
= 120 numbers. Out of them, each 24 will have 1, 2, 3, 4 & 5 as ten thousands, thousands, hundreds, tens & unit digit. 1 + 2 + 3 + 4 + 5 = 15 so face value of each column = 15*24 = 360. Sum = 360 (10,000 + 1,000 + 100 + 10 + 1) = 39,99,960.