We use cookies to personalise content and advertisements and to analyse access to our website. Furthermore, our partners for online advertising receive pseudonymised information about your use of our website. cookie policy and privacy policy.
 
+0  
 
0
47
3
avatar

How many positive, five-digit integers contain the three-digit block “123”? Two such integers are 12,350 and 41,232.

 Nov 5, 2019
 #1
avatar+105411 
+1

123  in the first through third positions,   we have  (00 - 99) in the last two positions  =  100 integers

 

123  in the second position through fourth positions,  we have  (1 - 9)  in the first position and  ( 0-9)  in the last position

So   9  * 10  =  90 integers

 

123 in the last three positions we have  (1 - 9)  in the first position and  (0 - 9)  in the second position

So  9 * 10  =  90 integers

 

So

 

100 + 90  + 90   =

 

280  integers

 

 

cool cool cool

 Nov 5, 2019
edited by CPhill  Nov 6, 2019
 #2
avatar
0

CPhill; The inadvertent typo of 180 should read 280.

 Nov 6, 2019
 #3
avatar+105411 
0

THX, guest  !!

 

Corrected  !!!!

 

 

 

cool cool cool

CPhill  Nov 6, 2019

11 Online Users

avatar
avatar