Question

50 ml of ethyl alchol and 40ml of water combined in a beaker add up to 90 ml of liquid

Answer 1

Answer:

I suppose the answer your teacher wants is 50+40 = 90 on the basis that 50 parts one liquid + 40 parts of another makes 90 total.

But let me let you in on the real world. Volumes, in almost all cases are NOT additive. Sometimes volumes add to give more than the total of the two and sometimes they give less. In particular, in the case of ethyl alcohol and water, they give less. If you take 50 mL of ethyl alcohol and add 50 mL water, the total volume will be about 96 mL and not 100.