All categories

4 years ago

Sally has $21.40 in dimes and quarters. There are 100 coins in all. How many of each coin does she have?

Mathematics

1 answer:

lyudmila [28]4 years ago

8 0

x = dimes

y = quarters

We also know:

Dimes: 0.10

Quarters: 0.25

100 = x + y

So, 0.10x + 0.25y = 100

And, y = 100 - x

Let’s use substitution:

0.10x + 0.25( 100 - x ) = 100

= 0.10x + 25 - 0.25x = 100

= 25 - 100 = 0.25x - 0.10x

= (-75) = 0.15x

x = (-75) divide by 0.15

x = (-500)

You might be interested in

If the points on a graph of a linear function are (-2,10 (0,4) (2,-2) and (4,8) what is the y-intercept

MatroZZZ [7]

Answer:

i think 5

Step-by-step explanation:

4 0

3 years ago

Read 2 more answers

If anyone answers ALL i will give all my points and will give Brainliest

Inga [223]

1: I can’t see one it’s cut out sorry :(
2:go down four horrizontal for each line making a rhombus
3: 3a:true 3b:true 3c:false 3D: false
4.PART A: Draw a square in the middle.
4. PART B: Say there are four right angles
5: Line, point, ray, line segment
6. There are 2 acute and 1 right
7. A B C
8: 1/4 1/6 1/8
9: 9a 9c and 9d
10: square and polygons first, then triangles because they have 4 sides while a triangle has 3
10 PART B: rectangles second, then the pentagons are third, the parallelogram is first, then the triangles because a rectangle has all right angles
11: she drew a square!
12: polygons without right angles
13: I can’t draw on your paper just draw three lines in the trapezoid
13: a c and d

6 0

3 years ago

Read 2 more answers

The following data were collected from 12 rain gauges in a park. Build a 95% CI for the mean rainfall at the park.

dybincka [34]

Answer:

Critical values: $t_{\alpha/2}=-2.201$ $t_{1-\alpha/2}=2.201$

95% confidence interval would be given by (3.646;4.472)

Step-by-step explanation:

1) Previous concepts

A confidence interval is "a range of values that’s likely to include a population value with a certain degree of confidence. It is often expressed a % whereby a population means lies between an upper and lower interval".

The margin of error is the range of values below and above the sample statistic in a confidence interval.

Normal distribution, is a "probability distribution that is symmetric about the mean, showing that data near the mean are more frequent in occurrence than data far from the mean".

The data is:

4.65 3.89 2.73 4.35 3.80 4.86 4.33 4.37 4.76 4.05 3.05 3.87

2) Compute the sample mean and sample standard deviation.

In order to calculate the mean and the sample deviation we need to have on mind the following formulas:

$\bar X= \sum_{i=1}^n \frac{x_i}{n}$

$s=\sqrt{\frac{\sum_{i=1}^n (x_i-\bar X)}{n-1}}$

=AVERAGE(4.65,3.89,2.73, 4.35, 3.8, 4.86, 4.33, 4.37, 4.76, 4.05, 3.05, 3.87)

On this case the average is $\bar X= 4.059$

=STDEV.S(4.65,3.89,2.73, 4.35, 3.8, 4.86, 4.33, 4.37, 4.76, 4.05, 3.05, 3.87)

The sample standard deviation obtained was s=0.6503

3) Find the critical value t* Use the formula for a CI to find upper and lower endpoints

In order to find the critical value we need to take in count that our sample size n =12 <30 and on this case we don't know about the population standard deviation, so on this case we need to use the t distribution. Since our interval is at 95% of confidence, our significance level would be given by $\alpha=1-0.95=0.05$ and $\alpha/2 =0.025$ . The degrees of freedom are given by: