<span> On the first day of Christmas,
my true love sent to me
A partridge in a pear tree. On the second day of Christmas,
my true love sent to me
Two turtle doves,
And a partridge in a pear tree. On the third day of Christmas,
my true love sent to me
Three French hens,
Two turtle doves,
And a partridge in a pear tree. </span>

The song continues, adding 4 calling birds on the 4th day, 5 golden rings on the 5th, and so on up to the 12th day, when 12 drummers add to the cacophony of assorted birds, pipers and lords leaping all over the place.

Notice that on each day there is one partridge (so I will have 12 partridges by the 12th day), and each day from the second day onwards there are 2 doves (so I will have 22 doves), and from the 3rd there are 3 hens (total of 30 hens), and so on.

So, how many presents are there altogether?

Partridges: 1 × 12 = 12

Doves: 2 × 11 = 22

Hens 3 × 10 = 30

Calling birds: 4 × 9 = 36

Golden rings: 5 × 8 = 40

Geese: 6 × 7 = 42

Swans: 7 × 6 = 42

Maids: 8 × 5 = 40

Ladies: 9 × 4 = 36

Lords: 10 × 3 = 30

Pipers: 11 × 2 = 22

Drummers: 12 × 1 = 12

Total = 364

We observe that we have the same number of partridges as drummers (12 of each); doves and pipers (22 of each); hens and lords (30 of each) and so on. So the easiest way to count our presents is to add up to the middle of the list and then double the result: (12 + 22 + 30 + 36 + 40 + 42) × 2 = 364.

3 0

3 years ago

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195/100 as a percentage?

nekit [7.7K]

The percentage of 195/100 is 195%

3 0

3 years ago

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A tour operator has a bus that can accommodate 20 tourists. The operator knows that tourists may not show up, so he sells 21 tic

dalvyx [7]

Answer:

The expected revenue of the tour operator is 985.

Step-by-step explanation:

There are two outcomes:

Either less than 21 tourists show up and the operator does not have to pay anything. Or 21 tourists show up and the operator has to repay 100.

Anyways, initially he gets the price of all the tickets sold. That is 21 each at 50, so $R = 21*50 = 1050$ .

Then, we need to find the probability that all of the 21 tourists show up. In this case, we have to subtract 100 from the revenue.

Each tourist has a 0.02 probability of not showing up. This means that each has a 1-0.02 = 0.98 probability of showing up. So the probability P that all 21 tourists show up is $P = (0.98)^{21} = 0.6542$ .

So, the expected revenue of the tour operator is

$R = 1050 - 100P = 1050 - 100(0.6542) = 984.58$

Rounded up, the expected revenue of the tour operator is 985.

6 0

3 years ago