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Bringing back an old one.... Making Toast

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Three slices of bread are to be toasted under a grill. The grill can hold two slices at once but only one side is toasted at a time. It takes 30 seconds to toast one side of a piece of bread, 5 seconds to put a piece in or take a piece out and 3 seconds to turn a piece over. What is the shortest time in which the three slices can be toasted?

Edited by BMAD

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On 4/17/2019 at 6:02 AM, rocdocmac said:
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116 seconds (or possibly even 106 seconds) presuming first two pieces are already in place.

Toasting alone takes 90 seconds for slices numbered 1, 2 and 3 with sides A and B.

Stages: (1) 1A  and 2A under grill (30 sec), followed by (2) 1B and 3A under grill (30 sec); finally (3) 2B and 3B under grill (30 seconds)

Normal additional time for single movements:

End of 1st stage: Slice 1 flipped from 1A to 1B (3 sec), 2A removed (5 sec), 3A inserted (5 sec)

End of 2nd stage: Slice 1 removed (5 sec.), slice 3 flipped from 3A to 3B (3 sec), slice 2 (2B) re-inserted with flip side up (5 sec)

End of 3rd stage: Done

Normal additional time = 26 seconds

Total time = 116 seconds.(1:56)

Exchange in one go:

If one is allowed to do simultaneous movements (exchanging in one switch of 5 sec), 10 seconds can be deducted, i.e. a total time of 106 seconds (1:46)

 

 

 

14 hours ago, Pirate8 said:

 

Left

side

 

Right

side

1-5

A1 in

 

6-10

B1 in

6-35

A1 toast

 

11-40

B1 toast

36-38

A flip

 

41-45

B out

39-68

A2 toast

 

46-50

C in

69-74

A out

 

51-80

C1 Toast

75-79

B2 in

 

81-83

C flip

80-109

B2 toast

 

84-113

C2 toast

110-114

B out

 

114-116

C out

         

Manual operations must not overlap.

 

 

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Spoiler

116 seconds (or possibly even 106 seconds) presuming first two pieces are already in place.

Toasting alone takes 90 seconds for slices numbered 1, 2 and 3 with sides A and B.

Stages: (1) 1A  and 2A under grill (30 sec), followed by (2) 1B and 3A under grill (30 sec); finally (3) 2B and 3B under grill (30 seconds)

Normal additional time for single movements:

End of 1st stage: Slice 1 flipped from 1A to 1B (3 sec), 2A removed (5 sec), 3A inserted (5 sec)

End of 2nd stage: Slice 1 removed (5 sec.), slice 3 flipped from 3A to 3B (3 sec), slice 2 (2B) re-inserted with flip side up (5 sec)

End of 3rd stage: Done

Normal additional time = 26 seconds

Total time = 116 seconds.(1:56)

Exchange in one go:

If one is allowed to do simultaneous movements (exchanging in one switch of 5 sec), 10 seconds can be deducted, i.e. a total time of 106 seconds (1:46)

 

 

Edited by rocdocmac
numbers corrected

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Spoiler

Starting the clock when placing the first two slices into the grill and stopping once the final slice is taken out... I get 2 mins, 39 secs

 

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Left

side

 

Right

side

1-5

A1 in

 

6-10

B1 in

6-35

A1 toast

 

11-40

B1 toast

36-38

A flip

 

41-45

B out

39-68

A2 toast

 

46-50

C in

69-74

A out

 

51-80

C1 Toast

75-79

B2 in

 

81-83

C flip

80-109

B2 toast

 

84-113

C2 toast

110-114

B out

 

114-116

C out

         

Manual operations must not overlap.

 

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On 4/18/2019 at 12:39 AM, Pirate8 said:

 

Left

side

 

Right

side

1-5

A1 in

 

6-10

B1 in

6-35

A1 toast

 

11-40

B1 toast

36-38

A flip

 

41-45

B out

39-68

A2 toast

 

46-50

C in

69-74

A out

 

51-80

C1 Toast

75-79

B2 in

 

81-83

C flip

80-109

B2 toast

 

84-113

C2 toast

110-114

B out

 

114-116

C out

         

Manual operations must not overlap.

 

Shouldn't the last entry (for C out) read 114-118?

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