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Lady bird [3.3K]
3 years ago
6

Simplify the following expression.

Mathematics
1 answer:
o-na [289]3 years ago
3 0

Answer:

i dont know what you mean but

3x(4x-3) simplified is 12x - 4 or 12x+(-4)

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How many minutes of news would the disc jockey have to play for every 60minutes of music
faust18 [17]
The same with this question you divide 60 by 6 and you get 5
3 0
3 years ago
Roberto rowed 20 miles downstream in 2.5 hours. The trip back, however, took him 5 hours. Find the rate that Roberto rows in sti
almond37 [142]

Answer:

<em>Roberto's speed in still water is 6 miles/hour and the river speed is 2 miles/hour</em>

Step-by-step explanation:

<u>Relative Speed</u>

When a body is moving at a constant speed v, the distance traveled in a time t is:

d=v.t

When Roberto rows downstream, his speed in still water is added to the speed of the water, making it easier to travel the required distance.

When Roberto rows upstream, his speed in still water is affected by the speed of the water, both are subtracted and the required distance is covered in more time.

Let's call

x = Roberto's rowing speed in still water

y = Speed of the river current

The speed when rowing downstream is x+y, thus the distance traveled is

d=(x+y).t_1

Where t1=2.5 hours. Substituting values:

20=(x+y)*2.5

Rearranging, we find the downstream equation:

2.5x+2.5y=20\qquad[1]

The speed when rowing upstream is x-y, and the distance traveled is

d=(x-y).t_2

Where t2=5 hours. Substituting values:

20=(x-y)*5

Rearranging, we find the upstream equation:

5x-5y=20\qquad[2]

Multiplying [1] by 2:

5x+5y=40

Adding this equation to [2]:

10x=60

Solving:

x=60/10=6

Dividing [2] by 5:

x-y=4

Solving for y

y=x-4=6-4=2

Thus, Roberto's speed in still water is 6 miles/hour and the river speed is 2 miles/hour

3 0
3 years ago
Which variable expression matches the word phrase? Column A Column B
erik [133]
<span>1. the sum of 12 and the quotient of 9 and a number

The responder's answer is not given but it can be 12 + (9 / n)

2. </span>the difference of 12 and the product of 9 and a number

The responder's answer would be <span>c. 12 – 9y

3</span>. the difference of 12 and the quotient of 9 and a number

The responder's answer would be <span>b. 12 – (9 ÷ y)
</span>
<span>4. 12 more than quotient of a 9 and number
</span>
The responder's answer would be<span> a. 12 + (9 ÷ y)</span>






4 0
3 years ago
In a race, a triathlete runs 1/3 of the total distance, cycles 2/5 of the total distance, and swims the remaining distance. He s
liraira [26]
4500 meters. You find this by adding 1/3 and 2/5 which equals 11/15. This means that the remaining 4/15 is 1200 meters long. Divide 1200 by 4 in order to find the distance per 1/15 and you get 300. Multiply 300 with 15 to get the total distance of the race.
5 0
3 years ago
Read 2 more answers
In the Salk vaccine field trial, 400,000 children were part of a randomized controlled double-blind experiment. Just about half
EastWind [94]

Answer:

Step-by-step explanation:

From the given information:

The number of children that were randomly allocated to each vaccination group; n₁ = 200,000

No of polio cases X₁ = 57

Now, in the vaccine group:

the proportion of polio cases is:

\hat p_1 = \dfrac{57}{200000}

=  0.000285

The number of children that were randomly allocated to the placebo group, n₂ = 200,000

No of polio cases X₂ = 142

In the placebo group

the proportion of polio cases is:

\hat p_2 = \dfrac{142}{200000}

Null and alternative hypothesis is computed as follows:

H₀: There is no difference in the proportions of polio cases between both groups.  

H₁: There is a difference in the proportions of polio cases between both groups.

Let assume that the level of significance ∝ = 0.05

The test statistic  can be computed as:

Z = \dfrac{\hat p_1-\hat p_2}{\sqrt{\dfrac{\hat p_1 \hat q_1}{n_1}+ \dfrac{\hat p_2 \hat q_2}{n_2}}}

Z = \dfrac{0.000285-0.000710}{\sqrt{\dfrac{0.000285(1-0.000285)}{200000}+ \dfrac{0.000710(1-0.000710)}{200000}}}

Z = \dfrac{-4.25\times 10^{-4}}{\sqrt{\dfrac{0.000285(0.999715)}{200000}+ \dfrac{0.000710(0.99929)}{200000}}}

Z = - 6.03

P-value =  2P(Z < -6.03)

From the Z - tables

P-value =  2 × 0.0000

= 0.000

We reject the H₀ provided that P-value is very less.

Therefore, we may conclude that there is a difference in the proportions of polio cases between the vaccine group and placebo group not due to chance.

7 0
2 years ago
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