All categories

3 years ago

I need help plz..... ☺

Mathematics

2 answers:

Kamila [148]3 years ago

4 0

It's 42, here's a quick trick to do this, so we know there's 7 movies, and to find the combination we know we can't choose 2 of the same movie, so to make this part easier , in your head take one movie from the stack out of the stack now there's 6 movies. It's now just the "plug and play" step , (7)*(6)=(42)
I'm sorry If this is to long of an explanation, but I hope that this helps you understand on how to do this problem. Have a nice day :)

Alex17521 [72]3 years ago

4 0

Use factorials to solve this question.

When you are choosing multiple items out of a set, the permutation formula will be represented by the following:

$\frac{n!}{(n-r)!}$

n represents the total amount of items, and r represents the number of items you're choosing from the set.

The stack has 7 items, and you are choosing sets of 2 items from the stack. Plug the values into the formula:

$\text{n = 7, r = 2}$
$\frac{7!}{(7-2)!} = \frac{7!}{5!} = \boxed{42}$

There will be 42 different combinations to choose from.

You might be interested in

Can atriangle be formed with side lengths of 5cm. 10cm and 15cm

andreyandreev [35.5K]

Theorem of cosine:
a²=b²+c²-2bc(cos α) ⇒cos α=-(a²-b²-c²) / 2bc

In this case:
a=15 cm
b=10 cm
c=5 cm

cos α=-(15²-10²-5²) / 2*10*5
cos α=-100 / 100
cos α=-1

A=arc cos -1=180º This is impossible, because:

A+B+C=180º; then B=C=0º This is impossible for make a triangle (B>0 and C>0 if we want to make a triangle).

Therefore: it is not possible can make a triangle with side lengths of 5 cm, 10 cm and 15 cm.

3 0

3 years ago

Read 2 more answers

use the general slicing method to find the volume of The solid whose base is the triangle with vertices (0 comma 0 ), (15 comma

lyudmila [28]

Answer:

volume V of the solid

$\boxed{V=\displaystyle\frac{125\pi}{12}}$

Step-by-step explanation:

The situation is depicted in the picture attached

(see picture)

First, we divide the segment [0, 5] on the X-axis into n equal parts of length 5/n each

[0, 5/n], [5/n, 2(5/n)], [2(5/n), 3(5/n)],..., [(n-1)(5/n), 5]

Now, we slice our solid into n slices.

Each slice is a quarter of cylinder 5/n thick and has a radius of

-k(5/n) + 5 for each k = 1,2,..., n (see picture)

So the volume of each slice is

$\displaystyle\frac{\pi(-k(5/n) + 5 )^2*(5/n)}{4}$

for k=1,2,..., n

We then add up the volumes of all these slices

$\displaystyle\frac{\pi(-(5/n) + 5 )^2*(5/n)}{4}+\displaystyle\frac{\pi(-2(5/n) + 5 )^2*(5/n)}{4}+...+\displaystyle\frac{\pi(-n(5/n) + 5 )^2*(5/n)}{4}$

Notice that the last term of the sum vanishes. After making up the expression a little, we get

$\displaystyle\frac{5\pi}{4n}\left[(-(5/n)+5)^2+(-2(5/n)+5)^2+...+(-(n-1)(5/n)+5)^2\right]=\\\\\displaystyle\frac{5\pi}{4n}\displaystyle\sum_{k=1}^{n-1}(-k(5/n)+5)^2$

But

$\displaystyle\frac{5\pi}{4n}\displaystyle\sum_{k=1}^{n-1}(-k(5/n)+5)^2=\displaystyle\frac{5\pi}{4n}\displaystyle\sum_{k=1}^{n-1}((5/n)^2k^2-(50/n)k+25)=\\\\\displaystyle\frac{5\pi}{4n}\left((5/n)^2\displaystyle\sum_{k=1}^{n-1}k^2-(50/n)\displaystyle\sum_{k=1}^{n-1}k+25(n-1)\right)$

we also know that

$\displaystyle\sum_{k=1}^{n-1}k^2=\displaystyle\frac{n(n-1)(2n-1)}{6}$

and

$\displaystyle\sum_{k=1}^{n-1}k=\displaystyle\frac{n(n-1)}{2}$

so we have, after replacing and simplifying, the sum of the slices equals

$\displaystyle\frac{5\pi}{4n}\left((5/n)^2\displaystyle\sum_{k=1}^{n-1}k^2-(50/n)\displaystyle\sum_{k=1}^{n-1}k+25(n-1)\right)=\\\\=\displaystyle\frac{5\pi}{4n}\left(\displaystyle\frac{25}{n^2}.\displaystyle\frac{n(n-1)(2n-1)}{6}-\displaystyle\frac{50}{n}.\displaystyle\frac{n(n-1)}{2}+25(n-1)\right)=\\\\=\displaystyle\frac{125\pi}{24}.\displaystyle\frac{n(n-1)(2n-1)}{n^3}$

Now we take the limit when n tends to infinite (the slices get thinner and thinner)

$\displaystyle\frac{125\pi}{24}\displaystyle\lim_{n \rightarrow \infty}\displaystyle\frac{n(n-1)(2n-1)}{n^3}=\displaystyle\frac{125\pi}{24}\displaystyle\lim_{n \rightarrow \infty}(2-3/n+1/n^2)=\\\\=\displaystyle\frac{125\pi}{24}.2=\displaystyle\frac{125\pi}{12}$

and the volume V of our solid is

$\boxed{V=\displaystyle\frac{125\pi}{12}}$

3 0

3 years ago

Evaluate -6-(-5) x (-9)

Rom4ik [11]

9.
That’s the answer

3 0

2 years ago

Read 2 more answers

A car is speeding at 60 miles per hour along a winding coastal highway. (The posted speed limit is 45 miles perhour). The speedi

Dmitry [639]

<span>8 minutes 20 seconds. First, lets determine who many miles per minute each vehicle moves by dividing each speed by 60. Speeder = 60 / 60 = 1 mile per minute. Police = 75 / 60 = 1.25 miles per minute. Other car = 45 / 60 = 0.75 miles per minute. Since the speeding car moves for 5 minutes before the police start to chase, that means that the speeding car will now be 5 + T miles down the road with T being the time the police has been chasing. The police will be 1.25 T. We're looking for when those two equations equal each other. So 5 + T = 1.25 T Subtract T from both sides 5 = 0.25T Divide both sides by 0.25 20 = T So it will take the police officer 20 minutes to catch up to the speeder. And they will both have traveled a total distance of 25 miles from the point where the speeder passed the police car. Now we need to figure out how far the law obeying car has moved during those 25 minutes. So 25 * 0.75 = 18.75 miles. The distance the law obeying car needs to travel to catch up to the police officer then becomes 25 - 18.75 = 6.25 miles. The number of minutes that the law obeying car needs to travel that distance is 6.25 / 0.75 = 8.333.... Which is 8 minutes 20 seconds.</span>

8 0

3 years ago

Is this equation an identity? tanx=sinx/cos x

ElenaW [278]

Yes........its an identity

7 0

3 years ago

Read 2 more answers