Answer:
Step-by-step explanation:
You can split the coins into 3 groups, each of them has 3 coins. Weigh group 1 vs group 2, if one is lighter, that group has the fake coin. If both groups weigh the same, then group 3 has the fake coin.
Continue to split the group that has the fake coin into 3 groups, each group has 1 coin. Now apply the same procedure and we can identify the fake coin.
Total of scale usage is 2
b) if you have 
coins then you can apply the same approach and find the fake coin with just n steps. By splitting up to 3 groups each step, after each step you should be able to narrow down your suspected coin by 3 times.
Step 1: you narrow down to group of 
coins
Step 2: you narrow down to group of 
coins
Step 3: you narrow down to group of 
coins
...
Step n: Step 1: you narrow down to group of 
coin
Answer:
(160, 36)
Step-by-step explanation:
Distance is always positive because, well, you aren't -50 meters away from your house or something. You are just 50 meters away from your house. And 160 is the distance between -6 and 154, because there is one minus and one plus, you add them, because that is how far they are apart, and then-43 and -7 were easy just subtract them.
20 + 40x = 260
40x = 260 - 20
40x = 240
x = 240/40
x = 6 fulltime employees needed
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Since 6 is greater than 5 you input it into the last equation!
2•(6^2) -7
2•(36) -7
72 -7
65
The answer is 65!
