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


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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

	$o k s i r . . . . . {T h a t}^{'} s t h e s a m e t h i n g I$ $g o t . . .$ $T h a n k s f o r y o u r s o l u t i o n$
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