Can you figure out these logic questions?

Question

1)We want to cook some vegetables for a period of 9 minutes, with no breaks. However, the only timepieces available are a 4 minute egg timer and a 7 minute egg timer. Neither timer has any markings on it, so they can only be used for starting and stopping. How is it possible to measure a continuous 9 minute period by combing these two timers?

2)You have 10 bags of gold coins. The bag are numbered from 1 to 10. Each bag contains 10 coins, and each coin is supposed to with 1 ounce. However, you suspect that one of the bags is light. You have accurate wieghing scale available, but you will only be allowed to make one weighing with it. How can you figure out which bag has the light coins by making only one weighing with the scale?

I have heard of the last one but I can't remeber the answer. Can someone help.

Answer 1

1) start both timers. ther first one finishes and there is second one has three minutes left.
(0) (3)
Immediately start the first one again, when the second one finishes there is one minute on the first.
(1)(0)
Immediately start the second one and when the first runs out there will be six minutes left on the second one.
(0)(6)
Start the first one and there will be 2 minutes left on the second one when the first one finishes. Start cooking the vegtables now.
(0)(2)
Start the second timer again after it stops (it has already been running for 2 minutes and that's how long the vegtables have been cooking). Let the vegtables cook till the second timer runs out again 2 min + 7 min = 9 min.

2) Take one coin out of bag one, 2 coins out of bag two, 3 out of 3.... then weigh all the bags. You can then reverse calculate the bag that is light.

Answer 2

1) First, flip both hourglasses over and drop the egg into the water. When the four minute timer runs out, flip it again. When the seven minute timer runs out, flip it over. The egg has been cooking seven minutes. Now when the four minute timer runs out again (after eight minutes) flip the seven minute timer back over. Since the seven minute timer has been running only a minute between flips, there's a minute worth of sand left. And when that minute runs out, the egg will have been cooking for exactly nine minutes.

2) if the light coins are 9/10 of an ounce:

step 1: we name all the bag of gold coins as #1, #2, #3......#8, #9, and #10

step 2: we put 1 coin from bag #1, 2 coins from bag #2, 3 coins from bag #3.........8 coins from bag #8, 9 coins from bag #9, and 10 coins from bag 10 onto the scale. Find out the total weight.

step 3: the total weight should have been 1 ounce X

(1+2+3+4+5+6+7+8+9+10=55) = 55 ounces if all coins are the same (1 ounce each).

step 4: Subtract the total of step 2 from total of step 3.

Conclusion: If step 4 results 1/10 oz, then bag #1 is the one, if step 4 results 2/10 oz, then bag #2 is the one, if step 4 results 3/10 oz, then bag #3 is the one.......etc.

Answer 3

put the 7 minute timer all the way up and the four minute timer half way.

weigh a bag and then hold that one in one hand and measure the others in the other hand one at a time.

Answer 4

Turn the seven and four minute timers over at the same time. At the end of the four minutes, turn the seven over and the four over. at the end of the three minutes (amount remaining on the 7) then turn the four over which will have one left at that point? Am i right? !!!

Answer 5

i've got faith that the desirable reaction is (a million) by using fact's logically sensible and existence like that that's greater suitable than a danger to be sure no count if or no longer 'A' is a Knight or Knave which will in turn be sure no count if or no longer there's a gold upon the island.

Answer 6

1) turn on the seven then right when its over put the 4 half way.

Answer 7

1 put the 7min althe way and the 4 miun one half way
2 weigh one then compare it too another one and another one til u find the light wieght one