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Alex_Xolod [135]

2 years ago

10

a researcher is studying the effects of playing chess on memory improvement. he identifies 50 people who play chess and 50 peopl

e who do not. each of the 100 people is given a questionnaire designed to determine memory level. none of the 100 people who participated in the study knew they were part of a study. which statement is true.

1 answer:

Sever21 [200]2 years ago

6 0

Answer:

Observational study

Step-by-step explanation:

Just took the test

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PLEASE HELP !!!!!!!!!!

umka21 [38]

Answer:

3 quarters

7 dimes and a nickel

7 dimes and 5 pennies

15 nickles

75 pennies

2 quarters 2 dimes and a nickel

etc.

Step-by-step explanation:

4 0

3 years ago

Noah is buying a pair of jeans and using a coupon for 10%off. The total price is $56.70 which includes $2.70 in sales tax. Noah’

lora16 [44]

Answer:

See below.

Step-by-step explanation:

So, we know that Noah's purchase can be modeled by the equation:

$x-0.1x+2.70=56.70$

Part 1)

The solution to the equation will be the value of x.

In this case, x will represent the original price of the jeans.

We know that Noah has a coupon for 10% off the <em>original price of the jeans</em>.

So, 0.1x will represent how much of the original price Noah gets a a discount on.

Therefore, (x - 0.1x) represents the total cost of the jeans <em>after</em> the coupon.

So, x is our original price of the jeans.

Part 2)

To verify that 70 is <em>not</em> a solution, we can simply substitute 70 for x and check whether or not the equation is true. So:

$(70)-0.1(70)+2.7\stackrel{?}{=}56.70$

Multiply:

$70-7+2.7\stackrel{?}{=}56.7$

Subtract:

$63+2.7\stackrel{?}{=}56.7$

Add:

$65.7\neq56.7$

However, we <em>can</em> verify that 60 <em>is</em> the solution by substituting. So, substitute 60 for every x:

$(60)-0.1(60)+2.7\stackrel{?}{=}5.7$

Multiply:

$60-6+2.7\stackrel{?}{=}56.7$

Subtract:

$54+2.7\stackrel{?}{=}56.7$

Add:

$56.7\stackrel{\checkmark}{=}56.7$

So, 60 is indeed the solution and is the value of x.

So, this means that $60 was the original price of the jeans.

8 0

3 years ago

Read 2 more answers

I need help siwjjwnwnjsb ejwjennejejejene

makvit [3.9K]

The answer is 3 hope this helps

3 0

3 years ago

Marie, Shelia, and Martha bought snacks for a girl's sleepover. They each bought the items shown in the following table at the l

creativ13 [48]

Using a system of equations, it is found that the unit prices are:

$2.25 for a bag of chips.

$1.50 for a liter of pop.

$1.75 for a chocolate bar.

For the system:

x is the unit price of a bag of chips.

y is the unit price of liter of pop.

z is the unit price for a chocolate bar.

From the table, the equations are:

$2x + 2y + z = 9.25$

$3x + 4y + z = 14.50$

$x + 3y + 3z = 12$

Replacing the <u>first equation on the second and the third:</u>

$z = 9.25 - 2x - 2y$

$3x + 4y + z = 14.50$

$3x + 4y + 9.25 - 2x - 2y = 14.50$

$x + 2y = 5.25$

$x = 5.25 - 2y$

$x + 3y + 3z = 12$

$x + 3y + 3(9.25 - 2x - 2y) = 12$

$-5x - 3y = -15.75$

$5x + 3y = 15.75$

Since $x = 5.25 - 2y$ :

$5(5.25 - 2y) + 3y = 15.75$

$-7y = -10.5$

$y = \frac{10.5}{7}$

$y = 1.5$

Then:

$x = 5.25 - 2y = 5.25 - 2(1.5) = 2.25$

$z = 9.25 - 2x - 2y = 9.25 - 2(2.25) - 2(1.5) = 1.75$

The unit prices are:

$2.25 for a bag of chips.

$1.50 for a liter of pop.

$1.75 for a chocolate bar.

A similar problem, also solved using a system of equations, is given at brainly.com/question/14183076

4 0

3 years ago

THIS IS A 3-STEP QUESTION PLEASE ASWER ACCORDINGLY! THANKS !!!

mariarad [96]

A.
Let x = age of Samantha.
Then x - 2 = age of Emily,
and x + 2 = age of Lauren.

b.
x - 2 + x + x + 2 = 42

c.
x - 2 + x + x + 2 = 42

3x = 42

x = 14

x - 2 = 14 - 2 = 12

x + 2 = 14 + 2 = 16

The ages of the sisters are 12, 14, 16.

4 0

3 years ago