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3 years ago

Who created multiplication ?

1 answer:

4 0

Multiplication is a very old concept in math. So old that it dates back to ancient egypt, mesopotamia, etc. Each place probably came up with the concept on their own parallel to one another, or trade helped make the concept spread. It's very likely that the actual person who came up with the idea is unknown and won't be known since the concept is so ancient. It's like asking "who came up with the alphabet" which is an equally old concept.

Side note: multiplication is repeated addition. So if we added 3+3+3+3+3 to get 15, then we can say 3*5 = 12 as a shortcut. So its likely ancient peoples were adding the same number to itself over and over, leading them to develop a shortcut notation/method to get the answer quicker.

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A new test to detect TB has been designed. It is estimated that 88% of people taking this test have the disease. The test detect

Elodia [21]

Answer:

Correct option: (a) 0.1452

Step-by-step explanation:

The new test designed for detecting TB is being analysed.

Denote the events as follows:

D = a person has the disease

X = the test is positive.

The information provided is:

$P(D)=0.88\\P(X|D)=0.97\\P(X^{c}|D^{c})=0.99$

Compute the probability that a person does not have the disease as follows:

$P(D^{c})=1-P(D)=1-0.88=0.12$

The probability of a person not having the disease is 0.12.

Compute the probability that a randomly selected person is tested negative but does have the disease as follows:

$P(X^{c}\cap D)=P(X^{c}|D)P(D)\\=[1-P(X|D)]\times P(D)\\=[1-0.97]\times 0.88\\=0.03\times 0.88\\=0.0264$

Compute the probability that a randomly selected person is tested negative but does not have the disease as follows:

$P(X^{c}\cap D^{c})=P(X^{c}|D^{c})P(D^{c})\\=[1-P(X|D)]\times{1- P(D)]\\=0.99\times 0.12\\=0.1188$

Compute the probability that a randomly selected person is tested negative as follows:

$P(X^{c})=P(X^{c}\cap D)+P(X^{c}\cap D^{c})$

$=0.0264+0.1188\\=0.1452$

Thus, the probability of the test indicating that the person does not have the disease is 0.1452.

4 0

3 years ago

LOOK AT PICTURE,THEN ANWSER QUESTION, WHOEVER ANSWERS CORRECT I WILL MARK BRAINIEST!!

Gnom [1K]

Answer:
B. 4/11

Solution:
Gradient=(y1-y2)/(x1-x2)
Gradient=(6-2)/(4-(-7)) =4/11

3 0

3 years ago

Find the area of the surface. The part of the surface z = xy that lies within the cylinder x2 + y2 = 36.

rewona [7]

Answer:

Step-by-step explanation:

From the given information:

The domain D of integration in polar coordinates can be represented by:

D = {(r,θ)| 0 ≤ r ≤ 6, 0 ≤ θ ≤ 2π) &;

The partial derivates for z = xy can be expressed as:

$y =\dfrac{\partial z}{\partial x} , x = \dfrac{\partial z}{\partial y}$

Thus, the area of the surface is as follows:

$\iint_D \sqrt{(\dfrac{\partial z}{\partial x})^2+ (\dfrac{\partial z}{\partial y})^2 +1 }\ dA = \iint_D \sqrt{(y)^2+(x)^2+1 } \ dA$

$= \iint_D \sqrt{x^2 +y^2 +1 } \ dA$

$= \int^{2 \pi}_{0} \int^{6}_{0} \ r \sqrt{r^2 +1 } \ dr \ d \theta$

$=2 \pi \int^{6}_{0} \ r \sqrt{r^2 +1 } \ dr$

$= 2 \pi \begin {bmatrix} \dfrac{1}{3}(r^2 +1) ^{^\dfrac{3}{2}} \end {bmatrix}^6_0$

$= 2 \pi \times \dfrac{1}{3} \Bigg [ (37)^{3/2} - 1 \Bigg]$

$= \dfrac{2 \pi}{3} \Bigg [37 \sqrt{37} -1 \Bigg ]$

3 0

2 years ago

The number of people that belong to a certain social website is 412 and growing at a rate of 5% every month. How many members wi

umka21 [38]

Initial number of the people that belong to a certain social website is 412. It is growing at a rate of 5% every month. It means that every month the number of people is growing 1.05 times. We can calculate how many of them will there be in 9 months: 412 * 1.05^9 = 412 * 1.55 = 638.6. When we round to the nearest whole number: there will be 369 members.

8 0

3 years ago

Read 2 more answers

Mr. Gengel wants to make a shelf with boards that are 1 1/3 feet long. If he has

PilotLPTM [1.2K]

Answer:

At most Mr.Gengel can cut at most 13 pieces with half a foot left.

8 0

2 years ago