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Question Number 117866 by aurpeyz last updated on 14/Oct/20

h o w m a n y f o u r d i g i t n u m b e r s c a n b e

f o r m e d w i t h t h e d i g i t s 0 1 2 3 4 5 6 7 8

9 ?

Commented by mr W last updated on 14/Oct/20

w i t h r e p e t i t i o n :

1000, 1001, \dots, 9999

\Rightarrow 9999 - 999 = 9000 n u m b e r s

Commented by mhmoud last updated on 14/Oct/20

good

Commented by mr W last updated on 14/Oct/20

w i t h o u t r e p e t i t i o n :

\frac{9}{10} \times P_{4}^{10} = 4536 n u m b e r s

o r

P_{4}^{10} - P_{3}^{9} = 4536 n u m b e r s

Answered by 1549442205PVT last updated on 14/Oct/20

10^{4} - ∣ \overset{―}{0 abc} ∣= 10^{4} - 10^{3} = 10000 - 1000

= 9000

Answered by bobhans last updated on 14/Oct/20

9 \times 10^{3} = 9, 000

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