Each side of the model of 413s is rectangular shaped.
So, by this statement we got to know that the model is in cuboid shape.
Hence, its volume will be (length×width×height) cubic feet.
A score of 85 would be 1 standard deviation from the mean, 74. Using the 68-95-99.7 rule, we know that 68% of normally distributed data falls within 1 standard deviation of the mean. This means that 100%-68% = 32% of the data is either higher or lower. 32/2 = 16% of the data will be higher than 1 standard deviation from the mean and 16% of the data will be lower than 1 standard deviation from the mean. This means that 16% of the graduating seniors should have a score above 85%.
I'm sorry I'm too lazy to read all of that. However, I did get the main point. The river was going at 3 mph. Since he wanted to travel 10 miles upstream and downstream, you would have to subtract 20 by 3. This would mean he was going at a speed of 17 mph.
Bear in mind that multiplying anything, and anything whatsoever by 1, has a product of the anything itself.
so, let's multiply 2/3 by 1 then and check about,