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In a confrontation with battle droids, twelve Jedi engage in combat. Each Jedi can destroy 10 droids per minute. At the end of each minute, four Jedi retreat and are replaced by four Padawans, each of whom can destroy half as many droids as a Jedi per minute. After the last four Jedi retreat, the Padawans continue fighting the droids alone. At the end of the confrontation, a total of 720 battle droids are destroyed. Throughout the confrontation, all Jedi and Padawans fight at their full rates, with none incapacitated. How many minutes did the Padawans fight alone after the last Jedi retreated?

A. 3
B. 3.5
C. 6
D. 7
E. 10

Jedi are 12 & Padawans are 4 after each minute 4 Jedi leave
total droids are 720
rate of Jedi 10 and Padawans is 5
1st minute = 10*12 ; 120
2nd minute = 8*10+4*5 ; 100
3rd minute = 4*10 + 8*5 ; 80

in 1st four minutes droid destroyed are (120+100+80) ; 300
left with 720-300 ; 420
which will be destroyed by Padawans @ 12*5 ; 60 per minute
time it will take when Padawans are alone fighting ; 420/60 ; 7 minutes

OPTION D ; 7
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Jedi rate = 10 droids per min
Padawan rate= half of jedi rate = 5 droids per min
It begins with 12 jedi. Every minute 4 J replaced by 4 P until no J remains

Minute 1:
12 Jedi
Droids destroyed = 12*10=120

Minute 2:
8 Jedi and 4 Padawans
Droids destroyed = (8*10)+(4*5)=100

Minute 3:
4 Jedi and 8 Padawans
Droids destroyed = (4*10)+(8*5)=80

Droids destroyed till al Jedi left = 120+100+80=300
Remaining droids =720-300=420

Now only 12 Padawans fight alone.
Rate of 12 padawans =12*5=60 droids per minute

Time = Remaining droids/12 padawans rate = 420/60=7 minutes

D
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Bunuel
In a confrontation with battle droids, twelve Jedi engage in combat. Each Jedi can destroy 10 droids per minute. At the end of each minute, four Jedi retreat and are replaced by four Padawans, each of whom can destroy half as many droids as a Jedi per minute. After the last four Jedi retreat, the Padawans continue fighting the droids alone. At the end of the confrontation, a total of 720 battle droids are destroyed. Throughout the confrontation, all Jedi and Padawans fight at their full rates, with none incapacitated. How many minutes did the Padawans fight alone after the last Jedi retreated?

A. 3
B. 3.5
C. 6
D. 7
E. 10

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min1
12j
12 * 10 = 120 destroyed

min 2
8j 4p
8*10 + 4*5 = 100 destoryhed

min 3
4j, 8p
4*10 + 8*5 = 80 destroyed

min 4 onwards all padwna
remaining droids = 720 - 300 = 420
totaal p = 12
destoryed per min = 12 * 5= 60
mins fought alone = 420/60 = 7
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1 Jedi = 10 droids / min
1 Padawan = 5 droids / min

1st minute,
12 Jedi = 120 droids

2nd minute
8 Jedi + 4 Padawan = 80 + 20 = 100

3rd minute
4 Jedi + 8 Padawan = 40 + 40 = 80

Remaining Droid = 720 - (120 + 100 + 80) = 420

From 4th minute 12 Padawan kill 60 droids per minutes. Total time required = 420 / 60 = 7 minutes

Hence, Answer is Option D
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Start of the battle: -
Number of Jedi = 12
Number of droids destroyed = 10*12 = 120

After 1 minutes: -
Number of Jedi = 12 -4 = 8
Number of Padawans = 4
Number of droids destroyed = 10*8 + 5*4 = 100

After 2 minutes: -
Number of Jedi = 8 -4 = 4
Number of Padawans = 4+4 = 8
Number of driods destroyed = 10*4 + 5*8 = 80

After 3 minutes: -
Number of Jedi = 4-4=0
Number of Padawans = 8+4 = 12
Number of driods destroyed = 5*12 = 60

Total driods destroyed after the last Jedi retreated = 120 + 100 + 80 = 300

Let us assume that for n minutes Padawans fight alone

Number of driods destroyed / minutes = 5*12 = 60

300 + 60n = 720
60n = 720 - 300 = 420
n = 420/60 = 7

Padawans fought alone for 7 minutes after the last Jedi retreated.

IMO D
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Time in mins123456
J count12840
D killed by J12080400
P count0481212...
D killed by P020406060...
Total D killed120100806060...

After the first 3 minutes P fight alone and kill 60 D every minute

So 120 + 100 + 80 + 60*t = 720
60t = 720 - 300
t = 420/60 = 7

P fight alone for 7minutes

Answer D

Bunuel
In a confrontation with battle droids, twelve Jedi engage in combat. Each Jedi can destroy 10 droids per minute. At the end of each minute, four Jedi retreat and are replaced by four Padawans, each of whom can destroy half as many droids as a Jedi per minute. After the last four Jedi retreat, the Padawans continue fighting the droids alone. At the end of the confrontation, a total of 720 battle droids are destroyed. Throughout the confrontation, all Jedi and Padawans fight at their full rates, with none incapacitated. How many minutes did the Padawans fight alone after the last Jedi retreated?

A. 3
B. 3.5
C. 6
D. 7
E. 10

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JEDI CAN BE DIVIDED INTO GROUPS 3 OF 4 EACH COZ 4 ARE REPLACED EVERY MINUTES

JEDI=J
PADAWANS=P
dROIDS=D

MINUTES GROUP 1 GROUP 2 GROUP 3 TOTAL
1 40 40 40 120
2 40 40 20 P 100
3 40 20 P 20P 80 TOTAL D = 300
4 20P 20P 20P 60
AND 60/MINUTE IS THE RATE AT WHICH ALL 3 GROUP OF P WILL DESTROY D
420 BEING LEFT SO 7 MILUTES MORE WILL BE REQUIRED
Bunuel
In a confrontation with battle droids, twelve Jedi engage in combat. Each Jedi can destroy 10 droids per minute. At the end of each minute, four Jedi retreat and are replaced by four Padawans, each of whom can destroy half as many droids as a Jedi per minute. After the last four Jedi retreat, the Padawans continue fighting the droids alone. At the end of the confrontation, a total of 720 battle droids are destroyed. Throughout the confrontation, all Jedi and Padawans fight at their full rates, with none incapacitated. How many minutes did the Padawans fight alone after the last Jedi retreated?

A. 3
B. 3.5
C. 6
D. 7
E. 10

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Bunuel
In a confrontation with battle droids, twelve Jedi engage in combat. Each Jedi can destroy 10 droids per minute. At the end of each minute, four Jedi retreat and are replaced by four Padawans, each of whom can destroy half as many droids as a Jedi per minute. After the last four Jedi retreat, the Padawans continue fighting the droids alone. At the end of the confrontation, a total of 720 battle droids are destroyed. Throughout the confrontation, all Jedi and Padawans fight at their full rates, with none incapacitated. How many minutes did the Padawans fight alone after the last Jedi retreated?

A. 3
B. 3.5
C. 6
D. 7
E. 10

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Initially we have 12 Jedi, Every minute:
4 Jedi leave, replaced by 4 padawans
After 3 such minutes, all 12 Jedi have left and 12 padawans remain
Let x = minutes Padawans fight alone afterward

Droids destroyed:
1st minute:
12 Jedi -> 12.10 = 120

2nd min (8 jedi, 4 padawans):
8.10 + 4.5 = 80 + 20 = 100

3rd min(4 jedi, 8 padawans):
4.10 + 8.5 = 40 + 40 = 80

After than: 12 padawans for x mins
12.5.x = 60x

Total destroyed:
120 + 100 + 80 + 60x = 720
300 + 60x = 720
60x = 720
x = 7

Option D
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Let's figure out how many droids are being destroyed at the end of each minute.

First minute:
12*10 = 120
Second minute:
(12-4)*10+4*5= 100 destroyed, 220 total destroyed
Third minute:
(12-8)*10+8*5 = 80 destroyed, 300 total destroyed
Fourth minute:
(12-12)*10+12*5=60 destroyed, 360 total destroyed

Note that from the beginning of the fourth minute onwards, it was the padawans fighting alone. So now they must destroy 360 more drones which, at their rate of 60 per minute, can be accomplished in 6 more minutes. Final answer 6 + 1 = 7 minutes.
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We have J= 10D/min and 4J is replaced by 4P where P= 5D/min.
1st min= 12J (only J present)= 120D
2nd min= 8J + 4P= 80 + 20= 100D
3rd min= 4J + 8P= 40 + 40= 80D
At 4th min no J is left. Hence, till 3rd min we have 300D destroyed and 420D left which need to be destroyed by 12P= 60D/min
Hence, Time after J is over and all D is destroyed= 420/60= 7 min.
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12 Jedi for first 1 minute
8 Jedi + 4 Padawans for next one minute
4 Jedi + 8 Padawans for next one minute
12 Padawan for last t minutes
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in 1st min 12 jedi can kill 120 droids
in 2nd min 8 jedi and 4 pandavas kill 80+20=100 droids
in 3rd min 4 jedi and 8 pandavas kill 40+40=80 droids
from 4th min till 10 min 12 pandavas kill 420 droids.

this will add up to 720 droids

pandavas was fighting alone for 7 mins
answer= 7 mins
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1st minute
all will be jedi hence total 120 destroyed
2nd minute: 4 padwan + 8 Jedi - 100 destroyed
3rd minute - 8 padwan + 4 jedi - 80 destroyed
4th minute - all padwans remaining 400 droits
hence after 3rd minute
total 7 minute required to destroy 720 droits

Hence D
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In first minute: 12 Jedi --(12*10) =120
In second min: 8Jedi +4 Padawan---(8*10)+(4*5)=100
In third min: 4 Jedi + 8 Padawans---(4*10)+(8*5)=80

total remaining = 720-(120+100+80) =420
per min total by 12 padawans = 12*5 =60
time reqd =420/60 = 7

Ans D
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answer D

rate of 1 J = 10 per min
rate of 1 P = 5 per min

total droids = 720

the amount of total droids destroyed in x minutes after the last jedi retires is:
12*10 + 8*10 + 4*5 + 4*10 + 8*5 + 12*5*x = 720
solve to find
x = 7
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At the end of each minute, 4 jedi are replaced by 4 padawans
Rate of 4 jedi per minute = 4*10 = 40
Rate of 4 padawans per minute = 40/2 = 20

The 12 jedi can be divided into 3 groups of 4 jedi each for the sake of simplification:

MinuteRate of Group 1Rate of Group 2Rate of Group 3Total Droids destroyed
Minute 1404040120
Minute 2404020100
Minute 340202080
Total300
Minute 4 onwards20202060 per minute

Thus, till minute 3, total droids destroyed are 300 and after that 60 droids are destroyed per minute.
So, Remaining droids = 720 - 300 = 420
Padawans fought alone for 7 minutes (ie, 420/60 minutes).
Bunuel
In a confrontation with battle droids, twelve Jedi engage in combat. Each Jedi can destroy 10 droids per minute. At the end of each minute, four Jedi retreat and are replaced by four Padawans, each of whom can destroy half as many droids as a Jedi per minute. After the last four Jedi retreat, the Padawans continue fighting the droids alone. At the end of the confrontation, a total of 720 battle droids are destroyed. Throughout the confrontation, all Jedi and Padawans fight at their full rates, with none incapacitated. How many minutes did the Padawans fight alone after the last Jedi retreated?

A. 3
B. 3.5
C. 6
D. 7
E. 10

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With the given data, we can say that 120 droids were destroyed in the 1st minute, 80+20 in the second and 40+40 in the third minute. There are still 420 droids to be destroyed yet.

Given x number of days after the 3rd minute and 12 Padawans can destroy 60 droids in a minute

60x= 420 or x=7

Therefore, Option D
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