The graph shows the maximum absolute humiditythe maximum amount of wa

The units don’t play much of a role in this question. The units are the same and there’s no conversion needed, you only have percentage conversion.

I solved this on the back of the napkin without a calculator or the napkin. Of course I was casually looking on my phone without timing myself for the time pressure of the question but it is possible to solve it without the calculator. You should make a challenge for yourself to figure out how to solve every DI question without a calculator. I don’t mean to force yourself to do calculations in your head but figure out if there is a shortcut that would allow you to solve the question without doing calculations.

1. If you look at this scary equation you will notice that at the top you have 100,000 in the numerator and denominator is basically going to be 300×300. I don’t think you need to have a more precise calculation there.

This means the weight of air going to be 1.1 kg approx. Since it’s over 1 , and water vapor Weighs 40 g, it’s not going to be 4% it’s going to be approx 10% less than 4% but not quite as little as 3.2% which is 20% less.

I hesitated a little because it was slightly over 40 g but 40 to 41 It’s only a 2 1/2% change whereas from one to 1.1 is a 10% change. So the final answer would likely be slightly higher than 3.6. Maybe it’s 3.7 but still less than 4% and closer to 3.6%

The second question is fairly easy because you just look at the chart and you see the rate of change and it’s clearly greater because it’s exponential or at least it looks to me like that and that was the correct answer 😇

The key to this question was a good understanding between the numerator and denominator so you understand what happens when you divide a number by 1.1 or 0.9. Key for mental math.