krakow

11-21-2004, 04:12 PM

How many 4-digit numbers begin with an odd digid and end with an even digid?

250

500

2000

2500 [clap]

5000

250

500

2000

2500 [clap]

5000

View Full Version : 4-digid: odd _ _ even

krakow

11-21-2004, 04:12 PM

How many 4-digit numbers begin with an odd digid and end with an even digid?

250

500

2000

2500 [clap]

5000

250

500

2000

2500 [clap]

5000

danielman

11-21-2004, 05:45 PM

How many 4-digit numbers begin with an odd digid and end with an even digid?

250

500

2000

2500 [clap]

5000

possibilities for 3rd digit: 1, 3, 5, 7, 9 (total = 5)

possibilities for 2nd digit: 0,1,2,3...,9 (total =10)

possibilities for 1st digit: 0,2,4,6,8 (total = 5)

possible arrangements = 5*10*5 = 2500

250

500

2000

2500 [clap]

5000

possibilities for 3rd digit: 1, 3, 5, 7, 9 (total = 5)

possibilities for 2nd digit: 0,1,2,3...,9 (total =10)

possibilities for 1st digit: 0,2,4,6,8 (total = 5)

possible arrangements = 5*10*5 = 2500

neokeynesian

11-22-2004, 04:10 AM

I think u have just missed the 4th digit??

possibilities for 4rd digit: 0,2,4,6,8 (total = 5)-------------------5C1

possibilities for 3rd digit: 0,1,2,3,4,5,6,7,8, 9 (total = 10)--------10C1

possibilities for 2nd digit: 0,1,2,3,4,5,6,7,8, 9 (total = 10)--------10C1

possibilities for 1st digit: 1,3,5,7,9 (total = 5)--------------------5C1

5*10*10*5=2500

possibilities for 4rd digit: 0,2,4,6,8 (total = 5)-------------------5C1

possibilities for 3rd digit: 0,1,2,3,4,5,6,7,8, 9 (total = 10)--------10C1

possibilities for 2nd digit: 0,1,2,3,4,5,6,7,8, 9 (total = 10)--------10C1

possibilities for 1st digit: 1,3,5,7,9 (total = 5)--------------------5C1

5*10*10*5=2500

danielman

11-22-2004, 04:17 AM

I think u have just missed the 4th digit??

possibilities for 4rd digit: 0,2,4,6,8 (total = 5)-------------------5C1

possibilities for 3rd digit: 0,1,2,3,4,5,6,7,8, 9 (total = 10)--------10C1

possibilities for 2nd digit: 0,1,2,3,4,5,6,7,8, 9 (total = 10)--------10C1

possibilities for 1st digit: 1,3,5,7,9 (total = 5)--------------------5C1

5*10*10*5=2500

Ooops!! :o

You're so right... I forgot a digit... (sight)

possibilities for 4rd digit: 0,2,4,6,8 (total = 5)-------------------5C1

possibilities for 3rd digit: 0,1,2,3,4,5,6,7,8, 9 (total = 10)--------10C1

possibilities for 2nd digit: 0,1,2,3,4,5,6,7,8, 9 (total = 10)--------10C1

possibilities for 1st digit: 1,3,5,7,9 (total = 5)--------------------5C1

5*10*10*5=2500

Ooops!! :o

You're so right... I forgot a digit... (sight)

lorcar

11-22-2004, 09:52 AM

i would say in a different way...

4 digits: 10.000 number in total (0-9999)

let's take, as example, the 3 digit series (101-200)

all start with the odd digit, and HALF of the number end with an even digit. So the rate is 1/2.

BUT in our 4 digits series, ONLY HALF of the numbers start with an odd digit

So 1/2 * 1/2 = 1/4=0,25

0.25*10000= 2500

4 digits: 10.000 number in total (0-9999)

let's take, as example, the 3 digit series (101-200)

all start with the odd digit, and HALF of the number end with an even digit. So the rate is 1/2.

BUT in our 4 digits series, ONLY HALF of the numbers start with an odd digit

So 1/2 * 1/2 = 1/4=0,25

0.25*10000= 2500

lorcar

11-23-2004, 12:11 AM

i would say in a different way...

4 digits: 10.000 number in total (0-9999)

let's take, as example, the 3 digit series (101-200)

all start with the odd digit, and HALF of the number end with an even digit. So the rate is 1/2.

BUT in our 4 digits series, ONLY HALF of the numbers start with an odd digit

So 1/2 * 1/2 = 1/4=0,25

0.25*10000= 2500

sorry

something seems wrong

then 4 digits: from 1000 to 9999

then 9000 numbers.

starting with ODD

1000

3000

5000

7000

9000

for a total of 5000 numbers. Of these, half will have even digit at the end.

--> 2500

4 digits: 10.000 number in total (0-9999)

let's take, as example, the 3 digit series (101-200)

all start with the odd digit, and HALF of the number end with an even digit. So the rate is 1/2.

BUT in our 4 digits series, ONLY HALF of the numbers start with an odd digit

So 1/2 * 1/2 = 1/4=0,25

0.25*10000= 2500

sorry

something seems wrong

then 4 digits: from 1000 to 9999

then 9000 numbers.

starting with ODD

1000

3000

5000

7000

9000

for a total of 5000 numbers. Of these, half will have even digit at the end.

--> 2500