SOLUTION: Three brothers—Leo, Sam, and Jax—are sharing a supply of energy bars during a hike. Leo starts the trip with a backpack full of bars. He eats 3 1/2 bars. After eating them, the

Algebra ->  Percentage-and-ratio-word-problems -> SOLUTION: Three brothers—Leo, Sam, and Jax—are sharing a supply of energy bars during a hike. Leo starts the trip with a backpack full of bars. He eats 3 1/2 bars. After eating them, the      Log On


   



Question 1210591: Three brothers—Leo, Sam, and Jax—are sharing a supply of energy bars during a hike. Leo starts the trip with a backpack full of bars. He eats 3 1/2 bars. After eating them, the ratio of the bars he has left to the bars he started with is exactly 3:4. Sam then takes the remaining bars. He eats half of them plus half a bar more. Jax takes what is left. He eats half of that amount plus half a bar more. After Jax is finished, there are exactly 2 bars left in the backpack. How many energy bars did Leo start with?
Found 2 solutions by ikleyn, MathTherapy:
Answer by ikleyn(53742) About Me  (Show Source):
You can put this solution on YOUR website!
.
Three brothers—Leo, Sam, and Jax—are sharing a supply of energy bars during a hike. Leo starts the trip with a backpack
full of bars. He eats 3 1/2 bars. After eating them, the ratio of the bars he has left to the bars he started with is
exactly 3:4. Sam then takes the remaining bars. He eats half of them plus half a bar more. Jax takes what is left. He eats
half of that amount plus half a bar more. After Jax is finished, there are exactly 2 bars left in the backpack. How many
energy bars did Leo start with?
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Let X be the number of energy bars Leo did start with (the unknown value under the problem's question).

Leo eats 3.5 bars first.

The number of bars left is x-3.5.


Write the proportion as stated in the problem

    %28x-3.5%29%2Fx = 3%2F4.


From this proportion

    4x - 14 = 3x,

    4x - 3x = 14,

       x    = 14.


So, the answer to the problem's question is 14 energy bars.


You may check that this answer satisfies the problem's conditions,
Thus, all the problem's conditions are consistent and do not contradict each other.

At this point, the problem is solved completely.



Answer by MathTherapy(10801) About Me  (Show Source):
You can put this solution on YOUR website!
Three brothers—Leo, Sam, and Jax—are sharing a supply of energybars during a hike. Leo starts the trip with a backpack
full of bars. He eats 3 1/2 bars. After eating them, the ratio ofthe bars he has left to the bars he started with is
exactly 3:4. Sam then takes the remaining bars. He eats half ofthem plus half a bar more. Jax takes what is left. He eats
half of that amount plus half a bar more. After Jax is finished,there are exactly 2 bars left in the backpack. How many
energy bars did Leo start with?
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METHOD 1
Let the multiplicative factor be x
Since the ratio of the bars he has left to the bars he started with is exactly 3:4, then the number of bars
he has left is 3x, and the number of bars he started with is 4x
With the number of eaten bars being 3%261%2F2, or 3.5, we get: 4x - 3x = 3.5, and x = 3.5
This means that the number Leo starts with is 4(3.5) = 14. 

******
CHECK
******
Original number of bars: 14
Number eaten by Leo: 3.5
Number remaining after Leo ate 3.5: 14 - 3.5 = 10.5
Number left after Sam ate 1%2F2 of remainder, plus 1%2F2 bar:%281%2F2%2910.5+-+.5+=+5.25+-+.5+=+4.75
Number left after Jax ate 1%2F2 of NEW remainder, plus1%2F2 bar: %281%2F2%294.75+-+.5+=+2.375+-+.5+=+1.875

As seen above, a 2-bar end-result didn't ensue. So, itw's then decided to apply a different method.

METHOD 2
Let the number of bars Leo started with, be B
With matrix%281%2C3%2C+3%261%2F2%2C+or%2C+3.5%29 being eaten, remainder is: B - 3.5
With Sam eating 1%2F2 of remainder, plus 1%2F2 bar,remainder becomes: %281%2F2%29%28B+-+3.5%29+-+.5 = %28B+-+3.5+-+1%29%2F2 = %28B+-4.5%29%2F2
As Jax ate 1%2F2 of remainder, plus 1%2F2 bar, then NEW remainder becomes: %281%2F2%29%28%28B+-+4.5%29%2F2%29+-+.5 = %28B+-+4.5%29%2F4+-+.5 = %28B+-+4.5+-+2%29%2F4 = %28B+-+6.5%29%2F4
Since 2 bars are now left, we get: %28B+-+6.5%29%2F4+=+2                                                          
                                                           B - 6.5 = 8 ----Cross-multiplying 
   Original number of bars, or B = 8 + 6.5 = 14.5

OR

Some like to go from the end to the beginning. In other words, from the 2-bar end result to the original number of bars.
This is illustrated below.

End-Number of bars: 2
Number of bars before Jax ate 1%2F2 bar, plus 1%2F2 of remainder: %282+%2B+.5%29%2F%281%2F2%29 = (2.5)*2 = 5
Number of bars before Sam ate 1%2F2 bar, plus 1%2F2 of remainder: %285+%2B+.5%29%2F%281%2F2%29 = (5.5)*2 = 11
Number of bars before Leo ate 3.5: 11 + 3.5 = 14.5 

******
CHECK
******
Original number of bars: 14.5
Number eaten by Leo: 3.5
Number remaining after Leo ate 3.5: 14.5 - 3.5 = 11
Number left after Sam ate 1%2F2 of remainder, plus 1%2F2 bar:%281%2F2%2911+-+.5+=+5.5+-+.5+=+5
Number left after Jax ate 1%2F2 of NEW remainder, plus1%2F2 bar: %281%2F2%295+-+.5+=+2.5+-+.5+=+2

VOILA!!!

There's an obvious CONTRADICTION, as one method produces an orignal amount of 14, while the other finds
the count to be 14.5. As a result of this. there doesn't seem to be a SOLUTION to this problem, at all!!