A-number-of-four-different-digits-is-formed-by-using-the-digits-1-2-3-4-5-6-7-in-all-possible-ways-each-digit-occuring-once-only-find-how-many-of-them-are-greater-than-3400-

Question Number 26477 by NECx last updated on 26/Dec/17

A n u m b e r o f f o u r d i f f e r e n t

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

d i g i t s 1, 2, 3, 4, 5, 6, 7, i n a l l p o s s i b l e

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

o n l y . f i n d h o w m a n y o f t h e m a r e

g r e a t e r t h a n 3400

Answered by mrW1 last updated on 26/Dec/17

t y p e 1 : 3 X Y Y w i t h X = 4, 5, 6, 7

N_{1} = 4 \times 5 \times 4 = 80

t y p e 2 : Z Y Y Y w i t h Z = 4, 5, 6, 7

N_{2} = 4 \times 6 \times 5 \times 4 = 480

\Rightarrow N = 80 + 480 = 560

Commented by NECx last updated on 26/Dec/17

T h a n k y o u s o m u c h s i r b u t t h e

t e x t b o o k s a y s 520

Commented by mrW1 last updated on 26/Dec/17

I^{'} m q u i t e s u r e t h a t t h e a n s w e r i s 560 .

Commented by NECx last updated on 26/Dec/17

o k s i r \dots . . {T h a t}^{'} s t h e s a m e t h i n g I

g o t \dots

T h a n k s f o r y o u r s o l u t i o n

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