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Help with a test question?!!

S

slater01

Registered User
I can't figure out number 28 on the math portion of the Marine Gouge for some reason. Here's the question:

At a "mess night" there are only captains, 2nd lieutenants, and 1st lieutenants. If the total number of 2nd lieutenants and 1st lieutenants is 30, the total number of 2nd lieutenants and captains is 45, and the total number of 1st lieutenants and captains is 35, what is the total number of company grade officers at the mess night?

All that I need is the formula on how to do a problem like this. I haven't taken a Math class since '01 and my test is coming up. This is the only question that I'm having trouble with and if I get this I will feel pretty good going into the test. Thanks again, this website is a life-saver!
 
Fly Navy

Fly Navy

...Great Job!
pilot
Super Moderator
Contributor
x = 2nd Lts
y = 1st Lts
z = Capts

x + y = 30
x + z = 45
y + z = 35

Solve. It's a simple algebraic substitution problem, with just 3 variables as opposed to 2.
 
R

RHPF

Active Member
pilot
Contributor
2LT + 1LT = 30
2LT + CAPT = 45
1LT + CAPT = 35

Ok, since you have Captain on both #2 and #3, you know that the only reason #2 has 10 more than #3 is because there must be 10 more 2LTs than 1LTs.

Using that knowledge, subtract 10 from #1 (30-10=20). Divide by 2 as there are two groups (20/2 = 10). There is 10 1LTs. Add the 10 you removed (the difference) back to the 2LTs for a total of 20.

Now that you know there are 10 1LTs subtract that from #3 and you know there are 25 Capts.

There may be a better way, but I use this way, it makes sense to me and I get the right answer.
 
mmx1

mmx1

Woof!
pilot
Contributor
Fly Navy said:
x = 2nd Lts
y = 1st Lts
z = Capts

x + y = 30
x + z = 45
y + z = 35

Solve. It's a simple algebraic substitution problem, with just 3 variables as opposed to 2.
Click to expand...

No need to to substitute. The problem asks for x+y+z. Sum up the three equations, you get
2x + 2y +2z = 110

Divide in half, you get x+y+z=55
 
Jen

Jen

Wife of a Growler stud
x + y=30
x + z=45
y + z=35

Knowing this.. x=30-y; z=45-x; y=35-z
Plug it in...
x + (35-z) =30
x - z=-5

Now plug in what you have for z:
x -(45-x)=-5
x + x=40
2x=40
x = 20

plug the 20 in for x:
20 + z=45
z = 25

:D
 
S

slater01

Registered User
Wow. It really HAS been a while!! I'm just over-thinking everything and freaking out over this test. You'd think with a 4.0 average I'd figure this crap out.....Thank you again.
 
ChunksJR

ChunksJR

Retired.
pilot
Contributor
slater01 said:
At a "mess night" there are only captains, 2nd lieutenants, and 1st lieutenants. If the total number of 2nd lieutenants and 1st lieutenants is 30, the total number of 2nd lieutenants and captains is 45, and the total number of 1st lieutenants and captains is 35, what is the total number of company grade officers at the mess night?
Click to expand...

42.
 
M

mules83

getting salty...
pilot
PropStop said:
NERDS!!!
Click to expand...

got to add the picture with it....

nerds.jpg
 
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