Billy has 201 packages of postcards. Each package has 18 cards. Use rounding to estimate. About

Mathematics

1 answer:

Sergeeva-Olga [200]2 years ago

8 0

Billy has 3,618 cards
201 * 18 = 3,618
18 card per package
201 packages
3,618 cards all together

You might be interested in

An hourglass consists of two sets of congruent composite figures on either end. Each composite figure is made up of a cone and a

belka [17]

Answer: third option 268.8

Explanation:

For this kind of proble it is very important that you attach the figure because it contains important information to understand the question.

I have attached the figure for better understanding.

1) The top portion (and the bottom is congruent but rotated 180°) of the hourglass is a figure equivalent to a cylinder on top and a cone on bottom.

So the total volume contained in the top portion is the volume of a cylinder + the volume of a cone.

This is how you calculate the volume of the top portion:

1) The height of the cylinder is 54 mm - 18 mm = 36 mm

2) The formula for the volume of a cylinder is V = π (radius)^2 * height

radius = 8 mm
height = 36 mm

=> V = π(8mm)^2 * 36 mm = 2304π (mm)^3

3) The formula for the volume of a cone is V = (1/3)π(radius)^2 * height

radius = 8 mm
height = 18 mm

V = (1/3)π(8mm)^2 * 18 mm = 384π (mm)^3

4) The total volume of the top portion is volumen of the cylindrical part + voume of the cone:

Total voluem = 2304π (mm)^3 + 384π (mm)^3 = 2688π (mm)^3

5) To find the number of seconds it take until all of the sand has dripped to the bottom of the hourglass you have to divide the total volumen of sand by the rate:

time in seconds = total volume of sand / rate of dripping

time in seconds = [2688 π (mm)^3 ] / [10π (mm)^3 / s] = 268.8 s

That is the answer: 268.8 s

4 0

4 years ago

Read 2 more answers

A sample was taken of the salaries of four employees from a large company. the following are their salaries, in thousands of dol

Free_Kalibri [48]

For given sample of salaries of four employees, the variance of their salaries is: 26 thousands of dollars

The formula for the variance is,

$S^2=\frac{\sum (x_i - \bar{x})^2}{n-1}$

where,

$S^2$ = sample variance

$x_i$ = the value of the one observation

$\bar{x}$ = the mean value of all observations

n = the number of observations

For given question,

n = 4

First we find the mean of their salaries.

(33 + 31 + 24 + 36 ) / 4 = 31

So, $\bar{x}=31$

Using the formula for variance ,

$S^2=\frac{(33-31)^2}{4-1}+\frac{(31-31)^2}{4-1}+\frac{(24-31)^2}{4-1}+\frac{(36-31)^2}{4-1}\\\\ S^2=\frac{4}{3} + \frac{0}{3} + \frac{49}{3} + \frac{25}{3} \\\\S^2= \frac{4+49+25}{3}\\\\S^2=\frac{78}{3} \\\\S^2=26$