Permutation question (1 Viewer)

[HSC2014]

Q: How many even numbers less than 600 can be formed using the digits 2,3,4,5,7,9 (no repetition)?

My probability skills are very weak, can someone help me I tried drawing up a tree diagram to get an idea of how to approach the question, but it didn't help. (Ans: 36)

 

[namelyanonymous]

First thing to do is to seperate your working out into three sections: 1-Digit numbers, 2-Digit numbers and 3-Digit Numbers (remember that the number <600)

 

[braintic]

Q: How many even numbers less than 600 can be formed using the digits 2,3,4,5,7,9 (no repetition)?

My probability skills are very weak, can someone help me I tried drawing up a tree diagram to get an idea of how to approach the question, but it didn't help. (Ans: 36)

One digit nos: 2

Two digit nos: 2 ways of filling the last digit, then 5 ways of filling the first: 10 numbers

Three digit nos:
... Either first digit is 2 or 4 (2 ways), last digit is the other even no. (1 way), then 4 ways of filling the middle digit: 8 numbers
... Or first digit is 3 or 5 (2 ways), last digit is 2 or 4 (2 ways), middle digit is one of 4 possibilities: 16 numbers

2+10+8+16 = 36

 

[HSC2014]

Thanks guys Question proved to be really easy. For some reason yesterday I was thinking that 5 digit numbers could be < 600 haha Long day