If in fact this is the case, you can simply put sets of 2 in series. Assuming the overall resistance is the same over each strip, this will effectively apply 12V over each strip.
Next in the picture, input voltage is 24 Vdc, current is 2.8 A! The LED strips is quite hot soon!
Check below youtube Video, you will get more details.
That is not a good option for 12V DC LED Strip.