Permutation-Combination
Aptitude

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Q.

How many natural numbers less than a lakh can be formed with the digits 0, 6 and 9?

 A.

242

 B.

243

 C.

728

 D.

729

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Solution:
Option(A) is correct

The digits to be used are 0,c6 and 9.

The required numbers are from 1 to 99999.

The numbers are five digit numbers.

Therefore, every place can be filled by 0, 6 and 9 in 3 ways.

Total number of ways $= 3×3×3×3×3 = 3^5$

But 00000 is also a number formed and has to be excluded.

Total number of numbers $= 3^5 -1$

$= 243-1$

$= \textbf{242}$


(1) Comment(s)


Omi
 ()

The required numbers are from 1 to 99999. How?

The number as to be less than a lakh, so 9999 has to be there.