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inna [77]
2 years ago
3

Sana and Abha had 100 playing cards. Both of them lost 20 cards each. The product of the cards they now have is 900. How many ca

rds did Abha start with?
Mathematics
1 answer:
Nutka1998 [239]2 years ago
8 0
Let x equal the number of cards they have after they lost 20 each. 2x+40=100
2x=60
X=30
30 squared = 900
30+20=50

The answer is 50
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It has to be Timmy and it is 412.

Step-by-step explanation:

Uh I did it in my head and it is really hard to explain.

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2 years ago
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The number of species n found on islands typically increases with the area of the island A. Suppose that this relationship is su
Crazy boy [7]

Answer:

n(A) = n_1A^k

Step-by-step explanation:

Taking into account that the growth rate of the number of species on the island is proportional to the density of species (number of species between area of the island), a model based on a differential equation is proposed:

\frac{dn}{dA} = k\frac{n}{A}

This differential equation can be solved by the method of separable variables like this:

\frac{dn}{n} = k\frac{dA}{A} with what you get:

\int\ {\frac{dn}{n}}\ = k\int\ {\frac{dA}{A}}

ln|n| = kln|A|+C. Taking exponentials on both sides of the equation:

e^{ln|n|} = e^{ln|A|^{k}+C}

n(A) = e^{C}A^{k}

how do you have to n (1) = n_1, then

n(A) = n_1A^k

8 0
2 years ago
What is the value of x in the equation 0.7x – 1.4 = –3.5?
deff fn [24]

0.7x-1.4 =-3.5

 add 1.4 to each side

0.7x = -2.1

 x = -2.1 / 0.7

x = -3

 Answer is B -3

3 0
2 years ago
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What are the differences among an experiment, a study, and a survey? Complete the explanation of the differences by selecting th
artcher [175]

Answer:

The full question is

<em>What are the differences among an experiment, a study, and a survey? </em>

<em> </em>

<em>1. In an observational study, randomization of subjects ______ </em>

<em>A. occurs </em>

<em>B. does not occur </em>

We understand randomization as a random process of assigning experimental subjects to treatment groups. Through this process, we have more control about variables which are not related to the experiment.

In an observational study, the researcher doesn't change anything, he or she studies the events as they are, without using any randomization process.

Therefore, the right answer here is B.<em> </em>

<em />

<em>2. A survey _______ </em>

<em>A. poses no interference on subjects </em>

<em>B. makes inferences about a population </em>

<em> </em>A survey poses no interference on subjects, actually if it does, then that survey is not reliable. An important charactersitic of a survey is that it must be objective, that way it will be reliable enough to use it in the research.

Therefore, the right answer is A.

<em />

<em>3. In an experiment, ___________ to discern differences in a response variable. </em>

<em>A. treatment is imposed </em>

<em>B. inferences are made </em>

<em>C. randomization does not occur</em>

Experiments are characterized by having certain "stimulus" at least in one group of subjects, that way researches compare data sets to prove their hypothesis.

Therefore, the right answer here is A.

<em />

8 0
2 years ago
A certain ferry moves up and down a river between Town A and B. It takes the ferry two hours to travel to Town A and only an hou
Y_Kistochka [10]

Answer:

The distance between two cities is <em>60 miles.</em>

Step-by-step explanation:

Time taken to travel from B to A = 2 hours

Time taken to travel from A to B = 1.5 hours

Current speed = 5 mph

Let the speed of ferry in still water = <em>u</em> mph

When the ferry moves with the current, it will taken lesser time (i.e. A to B) and when it moves against the current it will take more time (i.e. B to A).

Let the distance between the two cities A and B = D miles

While moving with the current, speed = (u+5)\ mph

While moving against the current, speed = (u-5)\ mph

Formula for Distance = Speed \times Time

Distance traveled in each case is same i.e. D.

So,

D = (u+5) \times 1.5 = (u-5) \times 2\\\Rightarrow 1.5u+7.5=2u-10\\\Rightarrow 0.5u =17.5\\\Rightarrow u = \dfrac{175}{5}\\\Rightarrow u = 35 \ mph

Now,

D = (u+5) \times 1.5\\\Rightarrow D =(35+5) \times 1.5\\\Rightarrow D =(40) \times 1.5\\\Rightarrow \bold{D =60\ miles}

So, the distance between two cities is <em>60 miles.</em>

6 0
2 years ago
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