vmadan10 wrote:
Hey I have used the following approach, if you have any suggestions to how I can improve my method please feel free to HMU.
I started with finding numbers which can take the units place, (2,3,5,7)
Now we have to fill the other two places i.e. Hundreds, Tens place. We can use 9 digits to fill these places as we can't use the prime number in the units digit to fill it.
For the hundred place we cannot have the number '0' as the resultant number will not be a 3 digit number. So we can fill the hundreds place in 8 ways.
For the tens place we have to choose from the 9 digits available to us but we have already used a non-zero number to fill the hundreds place so there are another 8 ways to fill the tens place.
Once we tally up we get 8*8*4 (8 ways to fill the hundreds place)*(8 ways to fill the tens place)*(4 ways to fill the units place).
Regards,
Varun Madan
I understood your approach, mine was different and I am going wrong somewhere, Can you help me out? I am getting different solutions when I move from ten's to hundred's vs moving from hundred's to ten's
ten's to hundred's
----------------------------------------
starting with the constraint
for the units place - 4 ways
for ten's place = 10 ways - 1 for the Unit's place = 9 ways
for hundred's place= 10 ways - 1 way for 0 - 1 way for unit's place - 1 way for ten's place = 7
total = 7*9*4 = 252 ways.
hundred's to ten's
----------------------------------------
starting with the constraint
for the units place - 4 ways
for hundred's place= 10 ways - 1 way for 0 - 1 way for unit's = 8 ways
for ten's place = 10 ways - 1 way for hundred's - 1 way for ten's = 8 ways
total = 8*8*4 = 256 ways
I am obviously going wrong somewhere in the first method, can someone point it out?