FAA written exam; Interpolation is tripping me up
- Thread starter Rebel Lord
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Rebel Lord
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Matthew
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your example:
28.2 to 28.3 and you have 28.22.
You are 20% above 28.2. If you assume the next column over is linear, then you will come up with an answer that is 20% of the way between the 28.2 and 28.3 values.
To see the math, I can Google it for you.
edit: To do this in your head: 1630 to 1533. There is about a 100 point difference, so 20% is 20 points. Since the values get smaller, you subtract. 1630-20 = 1610.
28.2 to 28.3 and you have 28.22.
You are 20% above 28.2. If you assume the next column over is linear, then you will come up with an answer that is 20% of the way between the 28.2 and 28.3 values.
To see the math, I can Google it for you.
edit: To do this in your head: 1630 to 1533. There is about a 100 point difference, so 20% is 20 points. Since the values get smaller, you subtract. 1630-20 = 1610.
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Cooter
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Subtract the two numbers on the right. Divided by 10 to figure out how much each increment is worth then add back however many increments to the lower number, or subtract from the higher number whichever you choose. So if it was 28.22, you would multiply the increment by 2 then subtract that from 1630. Or multiply by eight and add that to 1533.
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murphey
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Best explanation yet - but be aware not every problem will work out this nicely.
Example:
28.5
28.51
28.6
What's the "distance" between 28.5 and 28.51? 10% of the distance between 28.5 and 28.6.
Now look at 1,340 and 1,244 and get the difference - 96.
What's 10% of 96? Well, we'd say it's 9.6 but you never know what the FAA thinks it is.
So take that 9.6 and add it to 1244 (because the 1244 corresponds to the 28.5) and get....1253.6
So look for 1253 or 1254 on the list of answers and choose that one.
BigBadLou
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Lou
Seems like a normal elementary school math problem.
Which part specifically is tripping you up?
Which part specifically is tripping you up?
murphey
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Well, more like freshman high school math, but think about it - when was the last time (other than an FAA exam) did you need interpolation to solve a problem?
James331
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I think there were some of those on my ATP test, I was good enough at doing a ruff estimate in my head, and there weren't too many of those questions for me to bother with the time consuming math.
dtuuri
Final Approach
It's math, but let me try to explain it without. Sooner or later, though, you need to drop in some numbers:
In the left column, you can think of each line as a certain distance, mileage marker for example, from the one above. So, you're part way between the markers. You're proprtionally the same distance along in the lane, er, column on the right. (sorry, I got carried away with my own analogy.
)
)dtuuri
write-stuff
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Haha... That's pretty good. Hadn't seen it.
Islandhopper
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Sometimes it's best skipping those if it's tripping you up. King Schools does a great way of teaching it in regards to the test.
wilkersk
Pattern Altitude
[flame suit] I answer all the easy questions first, then go back and count the ones that require me to get out the scratch paper. Its usually only 2 questions. So, I use the clock method. Hasn't failed me yet. And the scratch paper stays clean.[flame suit/]
Austin_Marshall
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Hahaha.... Perfect one, vontresc.
Sac Arrow
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BigBadLou
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I learned basic math, fractions and percentage in elementary school. (and further deepened my knowledge later and in HS) But then again, I went to a good school.
I use interpolation practically every day. And every time I fly. You might not realize it. If burn 8 gph and I intend to cruise 45 minutes, I interpolate the 8gph at 75% and get 6 gallons.
But yes, you can just use ForeFlight and it will give you full fuel burn and you don't need to even think about math.
But I like to keep my brain sharp so I do use math every day, without realizing it most of the time.It seems like the OP got discouraged by all the negative comments and left. Sucks. Come back, Rebel, you will find help in the end, you just have to sift through a lot of useless posts.
azpilot
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As far as answering questions like that on the test goes, you can usually toss out two of the answers pretty quickly and know which one is right without actually doing the math.
For example. Let's say the choices are:
A) 1645
B) 1523
C) 1611
You can exclude A and B right away because they don't fall between 1630 and 1533.
Or if they give you something like this:
A) 1545
B) 1611
C) 1510
You can look at that and notice right away that C isn't right, because it doesn't fall between the two. Next you notice that 28.22 is pretty close to 28.2, so you know that the resulting altitude should be pretty close to 1630. That makes B the right answer.
This isn't a test where you actually have to show your work. That is coming up in the Oral and practical test. Don't make it harder than it needs to be. This is just a multiple choice test. Use some of the test taking skills you learned when you were getting ready to take the SAT in highschool.
On top of that, there are only three answers to choose from. Usually one of the answers can be discounted very quickly, and the other can be discounted with a little bit of though. If you know two answers are wrong, the third must be right.
For example. Let's say the choices are:
A) 1645
B) 1523
C) 1611
You can exclude A and B right away because they don't fall between 1630 and 1533.
Or if they give you something like this:
A) 1545
B) 1611
C) 1510
You can look at that and notice right away that C isn't right, because it doesn't fall between the two. Next you notice that 28.22 is pretty close to 28.2, so you know that the resulting altitude should be pretty close to 1630. That makes B the right answer.
This isn't a test where you actually have to show your work. That is coming up in the Oral and practical test. Don't make it harder than it needs to be. This is just a multiple choice test. Use some of the test taking skills you learned when you were getting ready to take the SAT in highschool.
On top of that, there are only three answers to choose from. Usually one of the answers can be discounted very quickly, and the other can be discounted with a little bit of though. If you know two answers are wrong, the third must be right.
rachelk.tailwinds
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Here's another way to look at it...
Since you know there are 10 numbers between 28.2 and 28.3, then there must also be 10 numbers between 1630 and 1533.
It's easy to count what is between the left column since you are simply adding a 1/100ths place to the end of 28.2.
To find what the 10 numbers are between the right column, subtract 1533 from 1630 (this is what you have to work with in between the top and bottom numbers). That equals 97 so now divide it by 10 (which equals 9.7) since you know there has to be a number that aligns with each number on the left column.
In order to find out what each of those numbers is, start from the top and subtract 9.7 from each number as you go. Now you should have two full columns of numbers with a corresponding number on the other side. Since you are looking for 28.22, just look straight across to find that your answer is 1610.6.
Since you know there are 10 numbers between 28.2 and 28.3, then there must also be 10 numbers between 1630 and 1533.
It's easy to count what is between the left column since you are simply adding a 1/100ths place to the end of 28.2.
To find what the 10 numbers are between the right column, subtract 1533 from 1630 (this is what you have to work with in between the top and bottom numbers). That equals 97 so now divide it by 10 (which equals 9.7) since you know there has to be a number that aligns with each number on the left column.
In order to find out what each of those numbers is, start from the top and subtract 9.7 from each number as you go. Now you should have two full columns of numbers with a corresponding number on the other side. Since you are looking for 28.22, just look straight across to find that your answer is 1610.6.
Rebel Lord
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It clicked finally. I have no idea why it tripped me up because it really is pretty simple. Thanks for the help and sarcasm
Matthew
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What was it that made it click? It would be nice to know for the next time a question like this comes up.
Rebel Lord
Line Up and Wait
I literally just forgot about the whole thing. Came back and looked at it and was like "oh duh that's simple" guess that's why they tell you to sleep on it
Matthew
Touchdown! Greaser!
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azpilot
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I had a controls class in college (I majored in mechanical engineering). The professor was Chinese and a VERY thick accent. He was horrible. No knew could understand him. He tried to explain to us how to estimate data from a second order (or higher) polynimial function. The way he explained it was so complicated. When I tried to do it his way, I would just scratch my head. When I went home to do the homework, I just did the problems my way, and they all worked out. He was just a really bad teacher.
Sometimes we just have to figure things out on our own. Once you really understand what is going on, it makes the problems much simpler.
Glad you got it figured out!