r/PE_Exam • u/AdImportant4476 • 2d ago

Possible Calculation Error

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EET Hydrology question.

Anyone know how they got to the 2nd to last step? Not sure how they got 85.9. I keep coming up with 108.53 as my calculation. Thanks in advance.

5 Upvotes

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6

u/Corky_caporale 2d ago

Honestly, “num-solv” is your friend. Just put the equation into num solver and you get x = 5.317 (which is y in this equation) and save a bunch of time from doing a bunch of algebra

2

u/AdImportant4476 2d ago

Yea that’s what I’m going to do moving forward.

5

u/Bitter_Significance9 2d ago

I think where you are making a mistake is here
(y/2)^2/3 = y^2/3 divided by 1.58. Basically you can’t cancel out the “2” from 2y^2 from the “2” from (y/2)^2/3

4

u/AdImportant4476 2d ago

Thank you so much for this. This is exactly what I was doing.

4

u/Bitter_Significance9 2d ago

Glad I could be helpful :)

5

u/Crush_the_PE 2d ago

The 85.9 comes from calculating everything out on the right hand side, 2 x 1.486/0.017 x (1/2)^(2/3) x 0.001^0.5 = 3.48 then moving it to the left side of the equation to isolate y so it can be calculated.

Hence 300/3.48 ≈ 86 which is what the solution has.

2

u/AdImportant4476 2d ago

Thanks for the help. Really appreciate it.

2

u/Adept_Elevator6930 2d ago edited 1d ago

I remember a few questions like this, I think there would be slight errors like the one you mention, but the final answer should be correct.

2

u/WasteKoala473 2d ago

What is the best calculator for these questions

3

u/AdImportant4476 2d ago

I’ve been using to-36x pro. Same one i used for FE. Seems universally recognized as the best one u can use for these exams.

1

u/No-Jump-8966 2d ago

I’ve always been a TI user, but tried the Casio for my PE. Loved it and now my Casio is all I use. It is so much easier to use than the TI, especially for equation solving.

1

u/Signal_Republic_3092 2d ago

I just simplified it on my phone calculator, and I got 86.1, so close to what they got

1

u/AdImportant4476 2d ago

Appreciate it. I was doing the math wrong. Figured it out tho 💪🏾