Lesson: Word Problems with Fractions

Comment on Word Problems with Fractions

hi, I did it that way

since 2/5=28 then 1/5 =14

therefore. 14*5=70

would that be sufficient for the similar questions?

Thanks
greenlight-admin's picture

You're referring to the question at 2:20 in the video.

Yes, your calculations are correct. However, so that others can understand your rationale, we need to add a variable.

Let x = total number of students

So, 2/5 of x = number of boys

So, 2/5 of x = 28

We can conclude that 1/5 of x = 14

So, x = (5)(14) = 70

Would it not be simpler to use 1/3 as 0.3x of 12,000. Then taking 0.3 of 12 as 36 and rewriting the zero's? Would using your step by step approach be more advantageous for longer questions?

Thank you
greenlight-admin's picture

Sorry, I'm not 100% sure what you're asking.
Can you please elaborate?

In the meantime, I should mention that using 1/3 instead of 0.3 will yield an value that's CLOSE to the value you're looking for.
However, since 1/3 is a little bit greater than 0.3, this is not necessarily the best alternative.

That's all I'll say about that. I'll wait for further information from you first.

Cheers,
Brent

http://greprepclub.com/forum/a-satellite-is-composed-of-30-modular-units-each-of-which-2717.html
Please explain this for me. I couldn't grasp the explanation on the module
greenlight-admin's picture

Question link: http://greprepclub.com/forum/a-satellite-is-composed-of-30-modular-units...

Did you see my solution at https://greprepclub.com/forum/a-satellite-is-composed-of-30-modular-unit...?

If so, can you tell me where you're having difficulties?

Cheers,
Brent

Hello Brent,
Please can you explain a little more the following question, https://greprepclub.com/forum/a-satellite-is-composed-of-30-modular-units-each-of-which-2717.html
Thank you
greenlight-admin's picture

Question link: https://greprepclub.com/forum/a-satellite-is-composed-of-30-modular-unit...

Tricky question!

Here's my algebraic solution: https://greprepclub.com/forum/a-satellite-is-composed-of-30-modular-unit...

Please let me know if that helps.

Cheers,
Brent

Hi!
Can you please explain this question.
https://greprepclub.com/forum/kelly-took-three-days-to-travel-from-city-a-to-city-b-by-aut-3387.html

Hi Brent, I am having trouble with the satellite question (GRE practice question (difficulty level: 160 to 170) – Manhattan Prep) found at: https://greprepclub.com/forum/a-satellite-is-composed-of-30-modular-units-each-of-which-2717.html ...

I see your solution but cannot fully grasp the problem as it is presented. Is there a visual representation that you could display or maybe use terms more familiar than satellites and modules so that I can understand the way the satellites and modules are compartmentalized?

Thank you.
greenlight-admin's picture

Hi Brent,

I am little confused when we calculate the fraction of the money,

for example in the question : vashti received a gift of 36$...

here you have calculated every fraction *36$

But , there are some questions for example
1/4 *36=9$ and ther subtract this 9$ from the 36$ and are moving ahead . So my question is how could we know which process need to be followed.

ThanK You
greenlight-admin's picture

Questions that require you to first subtract a fractional amount before continuing will typically feature the word REMAINING.

Here's an example:
Joe has $60. If Joe spends 1/5 of his money on lunch, and then spends 1/3 of his REMAINING money on dinner, how much money does Joe have left?

Solution: 1/5 of $60 = $12 ($12 spent on lunch)
$60 - $12 = $48 (Joe has $48 REMAINING)

1/3 of $48 = $16 ($16 spent on dinner)
Amount of money left = $48 - $16 = $32

Answer: Joe has $32 left.

Does that help?

Thank you that really hepled me.

I don't understand both the satellite and kelly question in the reinforcement activity section.
greenlight-admin's picture

The satellite question: https://greprepclub.com/forum/a-satellite-is-composed-of-30-modular-unit...
This question is CRAZY difficult (only 28% correct!).
I've provided three different solutions to the satellite question. Have you had a chance to review all three solutions?
If so, can you tell me where I lost you?

The Kelly question: https://greprepclub.com/forum/kelly-took-three-days-to-travel-from-city-...
Did your review my solution?
I'm happy to elaborate on any points. Just tell me what you would like me to elaborate on.

Cheers,
Brent

The satellite question I got lost when you multiplied it by 30 and then added x.
greenlight-admin's picture

Let's look at the solution in which I assigned a NICE VALUE to the number of upgraded sensors.

GIVEN: The number of non-upgraded sensors on one modular unit is 1/5 the TOTAL number of upgraded sensors on the entire satellite
In other words: (# of non-upgraded sensors on ONE modular unit) = (1/5)(total # of upgraded sensors on the entire satellite)

So, let's say there's a TOTAL of 5 upgraded sensors on the entire satellite.
This means: (# of non-upgraded sensors on ONE modular unit) = (1/5)(5) = 1

Since there are 30 modular units altogether, the TOTAL number of non-upgraded sensors = (30)(1) = 30.

So, the TOTAL number of sensors = (total number of non-upgrades) + (total number of upgraded)
= 30 + 5
= 35

What fraction of the sensors on the satellite have been upgraded?
= 5/35
= 1/7
----------------------------------

Now let's examine the solution in which I assigned a VARIABLE to the number of upgraded sensors.

GIVEN: The number of non-upgraded sensors on one modular unit is 1/5 the TOTAL number of upgraded sensors on the entire satellite
In other words: (# of non-upgraded sensors on ONE modular unit) = (1/5)(total # of upgraded sensors on the entire satellite)

So, let's say x = the TOTAL number of upgraded sensors on the entire satellite.
This means: (# of non-upgraded sensors on ONE modular unit) = (1/5)(x) = x/5

Since there are 30 modular units altogether, the TOTAL number of non-upgraded sensors = (30)(x/5) = 6x

So, the TOTAL number of sensors = (total number of non-upgrades) + (total number of upgraded)
= 6x + x
= 7x

What fraction of the sensors on the satellite have been upgraded?
We have 7x sensors and x of them have been upgraded
= x/7x = 1/7

Does that help?

Cheers,
Brent

Yes that helped and for the kelly question the only problem i had was the third day. I don't understand where the negative signs are coming from?
greenlight-admin's picture

The first step in that solution was to assign a "nice" value to the total distance.
So, I let the TOTAL distance = 1 mile

This allows us to create the following word equation:
(distance traveled on Day 1) + (distance traveled on Day 2) + (distance traveled on Day 3) = 1 mile

From here, it's just a matter of plugging values into the first two sets of brackets.

Earlier in the solution we found that:
- Distance traveled on Day 1 = 2/5 miles
- Distance traveled on Day 2 = 2/3(1 - 2/5) miles

We can now substitute values into our word equation....
We get: (2/5) + [2/3(1 - 2/5)] + (distance traveled on Day 3) = 1
Subtract 2/5 from both sides of the equation: [2/3(1 - 2/5)] + (distance traveled on Day 3) = 1 - 2/5
Subtract [2/3(1 - 2/5)] from both sides of the equation: (distance traveled on Day 3) = 1 - 2/5 - [2/3(1 - 2/5)]
Answer: D

Does that help?

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