Question

in how many three digits number can be formed if
____a.there are no restrictions?
____b.all three digits is greater than 700?
____c.the number is less than 200?
____d.the number is greater than 700?
____e.the number is greater than 600 but greater than 400?
____f.the number is greater than 100,divisible by 5 and no two digits are the same?
____g.the number is less than 800 but greater than 400,is even and no two digits are repeated?

Answer 1

no restrictions? 1000

Answer 2

second one doesn't make any sense

Answer 3

second 1 300?

Answer 4

number is less than 200 first digit is oh wait. three digit number. ok so least it can be is 100

Answer 5

most it can be is 999

Answer 6

that is alot of questions to answer for free/one medal :)

Answer 7

there are 900 of them

Answer 8

yes no restriction sir

Answer 9

was that for me amistre??lol

Answer 10

now if it is less than 200 first digit is a 1
so you have 10 times 10 = 100 choices for last two

Answer 11

a. 810
b. 8
c. 100
d. 200
e. wrong question
f. 128
g. 120

Answer 12

well "no restrictions" is fine, but i don't call 002 a three digit number

Answer 13

ramkrishna???

Answer 14

if you think 002 counts as a three digit number, then there are 1000 of them, 000 through 999

Answer 15

002 is one digit number not 3 digit number

Answer 16

where is the 002?

Answer 17

i believe ur answes r wrong ramkrishna?

Answer 18

"satellite73" is talking about 002

Answer 19

ramkrishma e. question >> the number is less than 600 but greater than 400?

Answer 20

Akshay Budhkar all the answers are correct .
tell me if any particular answer is wrong and why?

Answer 21

answer of part e. 100

Answer 22

if the first digit has to be at least a 1, then doesnt that make 900 three digit numbers?
(for no restrictions)
9 possible numbers for first digit
10 for second
10 for third

Multiply and get 900?

Or do 999-100+1 = 900?

Answer 23

or am i reading that wrong.

Answer 24

lets do f)
greater than 100 means the first digit has 8 choices
divisible by 5 means last digit has two choices, 0 or 5
no two digits are the same means ...

good luck!

Answer 25

b is wrong ramkrishna

Answer 26

love to see a clear answer to f) but i am going for lunch. yikes

Answer 27

ok ok guys let see this example of my prof > how many three digitscan be formed from the numbers 1,2,3,4,5
____a.repetition is allowed?
____b.repetition is not allowed? ok<<<<this is the example

Answer 28

answer given by me for part a was wrong
correct answer
a. 900

Answer 29

try to answer the example of my prof

Answer 30

explanation for b)
since all the three digits should be greater than 7 so the possibilty of all the three places is 2.
so. 2*2*2=8

Answer 31

correct sir

Answer 32

if repetition is allowed, we have

5 possible choices for first digit
5 for second
5 for 3rd
5 for 4th
and 5 for 5th.

5*5*5*5*5 = 3125

Answer 33

how many three digitscan be formed from the numbers 1,2,3,4,5
____a.repetition is allowed?
____b.repetition is not allowed?
ans. a) 125
b) 60

Answer 34

i thought 5= (5)(4)(3)(2)(1)= 120

Answer 35

if repeatition is not allowed

Answer 36

if repetition isnt allowed we have:

5 choices for 1st number
4 for second
3 for third,
2 for 4th
1 for 5th.

thats 5! which is 120

Answer 37

im sorry guys got confused letter b question is here ____b.all three digits must be the same?

Answer 38

wow im just reading what i want to =/

Answer 39

ramkrishna is correct

Answer 40

b) 9

Answer 41

somehow i was thinking we needed a 5 digit number

Answer 42

if all three digits must be same then there are 9 possibility for the first place then the possibility for the remaning two places is 1. so 9*1*1=9

Answer 43

if you need explanation for any part then tell me.

Answer 44

joemath correct in repetion is not allowed

Answer 45

isn't (f) ... 135

Answer 46

How?

according to me since the number should be greater than 100 so first digit can be arranged in 8 possible ways.
and it should be divisible by 5 so the unit place should be either 0 or 5.
and now we left with only 8 digits since the repetition is not allowed
so 8*8*2=128

Answer 47

That doesn't work

Answer 48

if we didn't care about the number being greater than 100 we could do this

2 choices for the ones digit, 9 choices for the 10's digit and 8 choices for the 100's digit

that gives 2*9*8=144 possibilities

included in that are things we don't want like 100

so we are down to 143 choices

finally any number of the form 0X5 (0 in the 100's position and 5 in the 1's position) is not wanted ...there are 8 of these

143-8
135