Question

The area of a circle varies directly as the square of the diameter. The area of a circle whose diameter is 20 inches is 314 square inches. What is the area of a circle whose diameter is 5 inches?

Answer 1

diameter d=5inch

Answer 2

\[a=\pi (d/2)^2\]

Answer 3

area of a circlearea of a circle=πd^2/4

Answer 4

area is pi r squared not d

r=radius
d= diameter

Answer 5

@nincompoop please help bro

Answer 6

r=d/2

Answer 7

yes

Answer 8

A=πr^2=π(d/2)^2

Answer 9

ok so can we solve the problem

Answer 10

ya

Answer 11

help me solve it please?

Answer 12

ok i ampretty sure this is just a 20/314=5/x

Answer 13

1570=20x

Answer 14

1570/20=20x/20= 78.5=x

Answer 15

are there choices? i would go with 78.5

Answer 16

no choices :(

Answer 17

can you check one more?

Answer 18

sure

Answer 19

i could be completely wrong btw its 5:00 am here

Answer 20

tired

Answer 21

@ShadowLegendX could you help this guy and me?

Answer 22

Neglecting air resistance, the distance an object falls from rest varies directly with the square of the time of fall. If an object falls 16.1 feet during one second, how far will it fall in 2.5 seconds?

Answer 23

same thing, you try it this time

Answer 24

2.5x16.1???

Answer 25

no, first stack the object you dont know(x) on top of the other part you know: so x/2.5

Answer 26

and then add an = and stack the other one with the same unit on the same side you had with you rfirst

Answer 27

16.1/1 = x/2.5

Answer 28

x/2.5=16.1/1

Answer 29

yes either way works good job i didnt see it

Answer 30

same difference

Answer 31

and then cross multiply

Answer 32

ok then what?

Answer 33

oh man I never learned cross multiplying
i never liked it

Answer 34

its easy, what is 16.1x2.5?

Answer 35

and what is 1*x

Answer 36

wait isn't that what i asked in the beginning???

"2.5x16.1???"

Answer 37

yea but if you wanna learn it you gotta write it out

Answer 38

40.25/1=40.25=x

Answer 39

well this is the way i look at it

1 second = 16.1 feet
2.5 seconds = 16.1 feet times 2.5
(because 2.5 is 2.5 times as much as 1)

Is that right?

Answer 40

its right i gues it just may not work in some situations.im not one to judge about that cause i am a lil wierd with math i just create things in my head to make it easier, i got suspended in 5th grade for making my teacher look bad lol

Answer 41

haha
well thanks so the final answer should be 40.3 right?
since my answer has to be rounded to the tenth place

Answer 42

sure, just remeber i could be wrong....also is this algebra 1?

Answer 43

Algebra 2

Answer 44

I'm a Junior