It does not work that way. I encourage you to read up on the process you are trying to execute. It is best to understand what you are doing. This link describes how this stuff is calculated

http://www.brew365.com/technique_calculating_mash_water_volume.php.

Typically, your strike water will be a smaller amount of water than your sparge water. You are targeting a ratio of water to grain that best works for your system and the beer you are making. Sticking with one ration, say 1.5 quarts of water to 1 lb of grain, is a good way to start and later make adjustments when you know how it works. The formulas uses to calculate strike water take into consideration the grain absorption rate as well as other parameters.

Next you need to calculate the amount of sparge water you will need to get the preboil volume. You need to know how much will be left behind in the mash tun, what your boil-off rate is, how full you want your carboy and how much will be left behind in your kettle after you fill up your carboy to said level.

For example, on my system I leave behind a couple quarts in my mash tun, my boiloff rate is about .7 gallons an hour, I leave behind a couple quarts in my kettle that has the gunk from the boil and I fill my carboy to 5.5 gallons. So, I need a bit over 11 gallons of water to get to my fermentation volume of 5.5 gallons. My personal Mash / Sparge water calculator tells me I need 5.3 gallons of strike water and 6 gallons of Sparge water to achieve this.

At this point, you can simply divide 11.3 gallons by two and be done with it but there is a good chance you will not be making the beer you are hoping to.