3456

Probability Level 3

Find the number of integers between 3456 and 6000 exclusive in which no digit is repeated.


The answer is 1319.

Victor Loh by Victor Loh , 19, Singapore

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

2 solutions

Arkodipto Dutta
Mar 3, 2016

did the same way

1 Helpful 0 Interesting 0 Brilliant 0 Confused
Anabela Matoso
Nov 21, 2015

If the first 3 digits are 345, the fourth can be 7,8 or9 (In this situation we have 3 numbers); If the first 2 digits are 34, the third can be 6,7,8or 9 and the fourth can be any other than those already used (In this situation we have 4x7=28 numbers); If the first digit is 3, the second digit can be 5,6,7,8 or 9, the third can be any other than those already used and the fourth can be any other than those already used (In this situation we have 5x8x7 numbers); If the fisrt digit is 4 or five, we have 9 possibilities for the second digit, 8 possibilities for the third digit and 7 possibilities for the fifth digit (In this situation we have 2x9x8x7 numbers); The answer is 3+28+280+1008=1319

0 Helpful 0 Interesting 0 Brilliant 0 Confused

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...