Question:

The sum of $5$ digit numbers in which only odd digits occur without any repetition is

Updated On: Jun 23, 2023
  • $277775$
  • $555550$
  • $ 1111100 $
  • $6666600$
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The Correct Option is D

Solution and Explanation

The digits that make the numbers are $1, 3, 5, 7$ and $9$. The number of numbers with one of these in the first place $= 4!$. $\therefore$ The required sum of all the numbers $= 25\left(10^{4} + 10^{3} +10^{2} + 10 + 1\right)\times 4! $ $= 600 \times\frac{ 10^{5} -1}{10 -1 }$ $= 600 \times 11111$ $= 6666600$.
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Concepts Used:

Arithmetic Progression

Arithmetic Progression (AP) is a mathematical series in which the difference between any two subsequent numbers is a fixed value.

For example, the natural number sequence 1, 2, 3, 4, 5, 6,... is an AP because the difference between two consecutive terms (say 1 and 2) is equal to one (2 -1). Even when dealing with odd and even numbers, the common difference between two consecutive words will be equal to 2.

In simpler words, an arithmetic progression is a collection of integers where each term is resulted by adding a fixed number to the preceding term apart from the first term.

For eg:- 4,6,8,10,12,14,16

We can notice Arithmetic Progression in our day-to-day lives too, for eg:- the number of days in a week, stacking chairs, etc.

Read More: Sum of First N Terms of an AP