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jekas [21]
3 years ago
8

On an island there are 7 cities. Each two of them connected by a direct road. How many roads are there?

Mathematics
2 answers:
Shalnov [3]3 years ago
4 0

Answer:

21 roads

Step-by-step explanation:

If for each city, there would be 6 direct roads, for example from island 1, there would be 6 direct roads, one for each rest of the island, island 2,3,4,5,6,7.

But the path from island 1 to 2 would be the same as that from island 2 to 1, it would be one less for each island, therefore in total it would be:

6 + 5 + 4 + 3 + 2 + 1 = 21

21 roads in total

Gnoma [55]3 years ago
3 0

Answer:

21 roads

Step-by-step explanation:

If each two cities are connected by a direct road, to find the number of roads we just need to solve a combination of 7 choose 2, that is, we need to find all pairs of two cities among the 7 cities:

Combination of 7 choose 2 = 7! / (5! * 2!) = 7*6/2 = 21

So there is a total of 21 roads on the island.

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A random two -digit number (10-99)is drawn find each probability
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3 0
3 years ago
~~~30 POINTS!!!!! WILL CHOOSE BRAINLIEST ANSWER!!!! <3 <3<3<3~~~
NeTakaya
Ok assuming that when he buys the fabric, he cuts pieces off to make it fit, but doesn't sow them in other places to make up the lost area

so
first find the area of tablecloth he needs to buy
area=pir^2
diameter=32
d=2r
r=d/2
r=32/2=16
adds 5 inches extra
16+5=21
r=21
area of cloth=pi21^2
are of cloth=441pi
aprox pi=3.14
area=441 tmes 3.14
area=1384.74


buys cloth with width of 50 and legnth of x
so we need 2 things
1. area of cloth bought>area of tablecloth
2. legnth &width must both be greater or equal to the diameter of the tablecloth (so we can make a circle fit)

new diameter=32+5+5=42 (2 sides)
so
l and w must both be greater than or equal to 42
 
50l>1384.74
divide both sides by 50 to find legnth
l>27.6948
but the legnth must be also greater than or equal to 42
so make l=42 for min legnth
area of cloth bought=lw=42 by 50=42 times 50=2100

so we do

area wasted=area bought-area needed
area needed=area of tablecloth=1384.74
area bought=2100
area wasted=2100-1384.74
area wasted=715.26 in^2


answer is wasted area=715.26 square inches




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3 years ago
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