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Bunuel
At the start of Potions class, Hermione and Ron are each given a magical cauldron. Hermione’s cauldron contains 27 magic beans, and Ron’s contains 729. At the end of every 6 hours, the number of beans in Hermione’s cauldron instantly increases by 200 percent, and at the end of every 18 hours, the number of beans in Ron’s cauldron instantly increases by 800 percent. If no beans are taken from either cauldron, after how many hours from the start of the class will the two cauldrons first contain the same number of beans?

A. 18
B. 27
C. 30
D. 36
E. 54

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27 = 3^3

729 = 3^6

After 6 hours =
Hermione's cauldron (HC) = 3^4
Ron's cauldron (RC) = 3^6

After 12 hours

HC = 3^5
RC = 3^6

After 18 hours

HC = 3^6
RC = 3^8

After 24 hours
HC = 3^7
RC = 3^8

After 30 hours
HC = 3^8
RC = 3^8

Option C
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e

Hermiones triples ever 6 hrs so it multiplies by 27 every 18 hours. Ron's muktiokies by 9 everY 18 hrs
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Bunuel
At the start of Potions class, Hermione and Ron are each given a magical cauldron. Hermione’s cauldron contains 27 magic beans, and Ron’s contains 729. At the end of every 6 hours, the number of beans in Hermione’s cauldron instantly increases by 200 percent, and at the end of every 18 hours, the number of beans in Ron’s cauldron instantly increases by 800 percent. If no beans are taken from either cauldron, after how many hours from the start of the class will the two cauldrons first contain the same number of beans?

A. 18
B. 27
C. 30
D. 36
E. 54

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For Hermione - Bean will increase by 200% i.e. it will become 3 times. Similarly for Ron a 800% increase will mean 9 times after 18 years.
at 6, 12, 18, 24, 30, 36 hours ...H changes to= 27* 3ˆ(n) ; n will be 1,2,3,4,5, respectively.
at 18, 36, 54 hours, R changes to = 729* 9ˆm ; m will be 1, 2, 3 respectively.
Clearly our answer will be a multiple of 6.
So from options, we check at 18 hours, then 30 hours, etc
at 18 hrs: H=27*3ˆ3 = 729. while R=729*9ˆ1
at 30 hrs: H=27*3ˆ5 =729*3ˆ2, while R=729*9ˆ1.
Thus ans = 30 hours
C.
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Ans = 54
After every 6 hours, Hermione's beans increased by 3x, hence every 18 hours, it increased by 3^3 = 27x
After every 18 hours, Ron's beans increased by 9x

At 18 hours,
H = 27 (original) * 27
R = 729 * 9
we can break down 729 = 27* 27 for ease of calculation
Hence, R = 27*27*9
We have the 9x extra with Ron

We need H = R at t hours where
H = 27 * 3^t/6 = 3^3 * 3^t/6 = 3^(3+t/6)
R = 729 * 9^t/18

We take 9 = 3^2, which gives R = 3^6 * 3^t/9 = 3^(6+t/9)

Hence we get
3+t/6 = 6+t/9
t/6 - t/9 = 3
t/18 = 3
t = 54 hours

Bunuel
At the start of Potions class, Hermione and Ron are each given a magical cauldron. Hermione’s cauldron contains 27 magic beans, and Ron’s contains 729. At the end of every 6 hours, the number of beans in Hermione’s cauldron instantly increases by 200 percent, and at the end of every 18 hours, the number of beans in Ron’s cauldron instantly increases by 800 percent. If no beans are taken from either cauldron, after how many hours from the start of the class will the two cauldrons first contain the same number of beans?

A. 18
B. 27
C. 30
D. 36
E. 54

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Hermoine: 27, increases by 200% means after every 6 hours, it become 3 times its value.

Similarly Ron: 729, becomes 9 times after 18 hours.

If we try iteratively, after 5 occurrences of 6 hours, the value becomes same (729*9).

Hence (C) 30 is the answer
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Bunuel
At the start of Potions class, Hermione and Ron are each given a magical cauldron. Hermione’s cauldron contains 27 magic beans, and Ron’s contains 729. At the end of every 6 hours, the number of beans in Hermione’s cauldron instantly increases by 200 percent, and at the end of every 18 hours, the number of beans in Ron’s cauldron instantly increases by 800 percent. If no beans are taken from either cauldron, after how many hours from the start of the class will the two cauldrons first contain the same number of beans?

A. 18
B. 27
C. 30
D. 36
E. 54

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its a gp question
200% increase means = 3 times [(100%+200%) of x = 300% 0f x= 3x}
800% increase means = 9 times
27= 3^3
729= 3^6
hermionie series= 3^3, 3^3 . 3 , 3^3 . 3^2...... 1st tern= 3^3 common ratio= 3
ron series = 3^ 6, 3^ 6. 3^2, 3^6 3 ^ 4..... 1st term=3^6 common ration = 3^2

we write terms till 54th hour and see that at 54th hours the terms in both series match
Ans-E

or

nth term for hermionie= 3^3 3^(t/6)-----increase every hour
n th term for ron= 3^6 , 3^2(t/18)--------- increase every hour
3^3 3^(t/6) = 3^6 3^2 (t/18)
t= 54
Ans- E
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Harmione is having 27 beans= 3^3

Ron is having 729 beans = 3^6

Harmione beans increase by 200 percent once in every 6 hours: i.e. increases by 3 times
Suppose, No. of 6 hours cycle are x

Harmione beans in x no. of 6 hours cycle = (3^3) (3^x)= 3^(x+3)

Ron's beans increase by 800 percent in every 18 hours: i.e. increase by 9 times
i.e. after every 3x no. of 6 hours cycles, Ron's beans are= (3^6) 9^(x/3)= 3^(6 + (2x/3))

After how many hours Harmione's beans & Ron's bean become equal ==> 3^(x+3) = 3^(6 + (2x/3))
x+3 = 6 + (2x/3)
x-(2x/3) = 3
x/3 = 3 ==> x = 9

i.e. after 9 no. of six hours cycles beans become equal, i.e. 54 hours
Bunuel
At the start of Potions class, Hermione and Ron are each given a magical cauldron. Hermione’s cauldron contains 27 magic beans, and Ron’s contains 729. At the end of every 6 hours, the number of beans in Hermione’s cauldron instantly increases by 200 percent, and at the end of every 18 hours, the number of beans in Ron’s cauldron instantly increases by 800 percent. If no beans are taken from either cauldron, after how many hours from the start of the class will the two cauldrons first contain the same number of beans?

A. 18
B. 27
C. 30
D. 36
E. 54

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Answer C

Hermione
27 beans
6 hours 81 (multiple by 3 because 200%)
12 hr 243
18hr 729
24 hr 2187
30 hrs 6561

Ron's
729 beans
18 hrs 6561
between 18 hr and 36 hr was 6561

therefor at 30hr they were the same
Bunuel
At the start of Potions class, Hermione and Ron are each given a magical cauldron. Hermione’s cauldron contains 27 magic beans, and Ron’s contains 729. At the end of every 6 hours, the number of beans in Hermione’s cauldron instantly increases by 200 percent, and at the end of every 18 hours, the number of beans in Ron’s cauldron instantly increases by 800 percent. If no beans are taken from either cauldron, after how many hours from the start of the class will the two cauldrons first contain the same number of beans?

A. 18
B. 27
C. 30
D. 36
E. 54

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At the start of the conflict Hermione's cauldron contains 27 beans and Ron's contains 729 beans. After 6 hrs , Hermione's cauldron contains (1+2)*27 = 81 beans and Ron's still contains 729 . After 12 hours , Hermione - (3)*81 = 243 , Ron - 729 , after 18 hours , Hermione - 243*3 - 729 , Ron's - (1+8)*729 = 6561 , after 24 hours ,Hermione - 729*3 = 2187 , and after 30 hours it will be 2187*3 = 6561 which will be equal to Ron's 6561 beans.

So , after 30 hours from the start of the class will the two cauldrons first contain the same number of beans.

SO , C is the answer
- Bunuel
At the start of Potions class, Hermione and Ron are each given a magical cauldron. Hermione’s cauldron contains 27 magic beans, and Ron’s contains 729. At the end of every 6 hours, the number of beans in Hermione’s cauldron instantly increases by 200 percent, and at the end of every 18 hours, the number of beans in Ron’s cauldron instantly increases by 800 percent. If no beans are taken from either cauldron, after how many hours from the start of the class will the two cauldrons first contain the same number of beans?

A. 18
B. 27
C. 30
D. 36
E. 54

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Hermione cauldron becomes thrice for every 6 hours - it is given that 200% increase that means (1+200/100) which is 3 times

Similarly Ron cauldron becomes 9 times for every 18hrs

At the end of 18hrs Hermione cauldron becomes 729 & Ron cauldron becomes 729 *9

Whereas at the end of 30 hrs it becomes 729 *9 for each

Therefore answer is 30hrs

Bunuel
At the start of Potions class, Hermione and Ron are each given a magical cauldron. Hermione’s cauldron contains 27 magic beans, and Ron’s contains 729. At the end of every 6 hours, the number of beans in Hermione’s cauldron instantly increases by 200 percent, and at the end of every 18 hours, the number of beans in Ron’s cauldron instantly increases by 800 percent. If no beans are taken from either cauldron, after how many hours from the start of the class will the two cauldrons first contain the same number of beans?

A. 18
B. 27
C. 30
D. 36
E. 54

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An easy way to go about this is, 100% increase means it doubled (x2), 200% increase means it tripled(x3), lly 300% increase means it quadrupled (x4).

27-------6hrs-------|---------6hrs---------|----------6hrs--------|
27-------------------x3---------------------x3----------------------x3 = 27 x 27 = 3^6
729-----------------------------18hrs------------------------------|
729-----------------------------------------------------------------x9 = 729 x 9 = 3^8


in next 12 hrs it will become 3^6 x 3 x 3

so at 30 hrs they have same number of beans.
Bunuel
At the start of Potions class, Hermione and Ron are each given a magical cauldron. Hermione’s cauldron contains 27 magic beans, and Ron’s contains 729. At the end of every 6 hours, the number of beans in Hermione’s cauldron instantly increases by 200 percent, and at the end of every 18 hours, the number of beans in Ron’s cauldron instantly increases by 800 percent. If no beans are taken from either cauldron, after how many hours from the start of the class will the two cauldrons first contain the same number of beans?

A. 18
B. 27
C. 30
D. 36
E. 54

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After each 6 hours H beans multiplies by 3 & after each 18 hours R beans multiplies by 9. 729 is square of 27. let after n hours from the start of the class both would be equal so 27 * 3^(n\6) = 729*9^(n/18). from option n would be 54. Ans option E.
Bunuel
At the start of Potions class, Hermione and Ron are each given a magical cauldron. Hermione’s cauldron contains 27 magic beans, and Ron’s contains 729. At the end of every 6 hours, the number of beans in Hermione’s cauldron instantly increases by 200 percent, and at the end of every 18 hours, the number of beans in Ron’s cauldron instantly increases by 800 percent. If no beans are taken from either cauldron, after how many hours from the start of the class will the two cauldrons first contain the same number of beans?

A. 18
B. 27
C. 30
D. 36
E. 54

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Bunuel
At the start of Potions class, Hermione and Ron are each given a magical cauldron. Hermione’s cauldron contains 27 magic beans, and Ron’s contains 729. At the end of every 6 hours, the number of beans in Hermione’s cauldron instantly increases by 200 percent, and at the end of every 18 hours, the number of beans in Ron’s cauldron instantly increases by 800 percent. If no beans are taken from either cauldron, after how many hours from the start of the class will the two cauldrons first contain the same number of beans?

A. 18
B. 27
C. 30
D. 36
E. 54

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For Hermione, we can formulate her exponential growth as: \(27*3^a=3^3*3^a=3^{a+3}\), where a is jumps of 6 hours.

For Ron, we can formulate his exponential growth as: \(27^2*9^b=3^6*3^{2b}=3^{6+2b}\) where b is jumps of 18 hours. Thus \(b=3a\).

We can set these two equal to each other.

\(3^{a+3}=3^{6+2b}\)

Bringing down the exponents, we get:

\(a+3=6+2b\)

\(a+3=6+2(3a)\)

\(a=-3/5\)

Since all the answer options are integers, the answer needs to be divisible by both 3 and 5. 30 is the only answer that satisfies that, therefore answer is C.
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H = 27 = 3^3
R = 729 = 3^6

H:
6 hours -> 3 times (200% increase)
18 hours -> 3*3*3

R:
18 hours -> 9 times (800% increase)

after 18 hours:
H:R
3^6 : 3^8

After 12 more hours (it is said as instant increase, so we dont consider R's increase over the time)
H:R
3^8: 3^8

18 + 12 =30 hours

ans: option C
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Never thought that those nostalgic childhood days with so much craze for Harry potter will finally pay off in my MBA preps.

Understanding the growth:

Step 1: Hermione Starts .
with 27 beans = 3^3
Every 6 hours, beans increase by 200%, i.e., they become 3 times as many.
After t hours: Hermione=(3^3)×(3^(t/6))
=3^(3+t/6)

Ron Starts with 729 beans = 3^6
Every 18 hours, beans increase by 800%, i.e., they become 9 times as many
Since 9=3^2, after t hours: Ron=(3^6)×(3^2 )^(t/18)=3^(6+t/9)

So these two were equal:

3^(3+t/6) = 3^(6+t/9)
So equate exponents: (3 + t/6) = (6 + t/9)
Solving for t we get t=54
Ans : E

Bunuel
At the start of Potions class, Hermione and Ron are each given a magical cauldron. Hermione’s cauldron contains 27 magic beans, and Ron’s contains 729. At the end of every 6 hours, the number of beans in Hermione’s cauldron instantly increases by 200 percent, and at the end of every 18 hours, the number of beans in Ron’s cauldron instantly increases by 800 percent. If no beans are taken from either cauldron, after how many hours from the start of the class will the two cauldrons first contain the same number of beans?

A. 18
B. 27
C. 30
D. 36
E. 54

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From given information:
The number of Hermione's beans x3 every 6 hours
The number of Ron's beans x9 every 18 hours

So when Ron's beans increase 1 time, Hermione's beans increase 3 times

Let a be the number of times that Ron's beans increase until his beans are equal to Hermione's beans
Hence 3a is the number of times that Hermione's beans increase

27*3^(3a) = 729*3^(2a)
<=> 3^3 * 3^(3a) = 3^6 * 3^(2a)
<=> 3+3a = 6+2a => a = 3

Total hours = 3*18 = 54

Answer: E
Bunuel
At the start of Potions class, Hermione and Ron are each given a magical cauldron. Hermione’s cauldron contains 27 magic beans, and Ron’s contains 729. At the end of every 6 hours, the number of beans in Hermione’s cauldron instantly increases by 200 percent, and at the end of every 18 hours, the number of beans in Ron’s cauldron instantly increases by 800 percent. If no beans are taken from either cauldron, after how many hours from the start of the class will the two cauldrons first contain the same number of beans?

A. 18
B. 27
C. 30
D. 36
E. 54

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imo C
Both cauldrons undergo exponential growth, Hermione at 3^(t/6+2) and Ron at 3^(t/9+4)
i.e. the first whole interval where t/6+2 and Roundown(t/9)+4 equal each other is when t is 30
so Hermione reaches the same amount beans as Ron after 30 hrs or 7 intervals.
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