i need 750 k ohm resistance in my circuit..
but i have not that resistance..
can i use a 670 k ohm and 100k ohm in series to achieve that.. i know that the theory says resistance get added when connected in series.. does it practically works?

 

Yes, it really works. You only have to be careful that one resistor is not getting too hot by using P=IE to find the power in each resistor.

 

i need to connect 750k ohm resistance to the two pin(osc 1 and osc 2) of HT12E encoder IC.. would it work..?

 

All I get for HT12E is Chinese characters. Can you post a datasheet?

 

or parallel 2 x 1.5m ohm

 

http://octopart.com/ Is an excellent source for data sheets. You will find the data sheet there for HT12E. I just looked at it.

 

Yes.

 

i need 750 k ohm resistance in my circuit..
but i have not that resistance..
can i use a 670 k ohm and 100k ohm in series to achieve that.. i know that the theory says resistance get added when connected in series.. does it practically works?

Yes, but it will give you 770k ohm, not 750k. Is that okay? A 670k and an 82K in series would be closer.