Question

The cost of a cell phone bill (C) increases when the number of text messages (T) increases. Write the correct equation for this scenario and solve for the cost when the number of texts is 4.

Texts Cost
5 2
10 4

A.C=10/T; C=20

B. C=10/T; C=5

C. C=.8T; C=16

D. C=.4T; C=1.6

Answer 1

try plugging in 10 for T
into each option and see if C = 4
if it doesn't then it can not be that option.

Answer 2

wait no sorry im wrong

Answer 3

\(\bf \begin{array}{cccllll}
\textit{something }&\textit{varies directly to }&\textit{something else}\\ \quad \\
\textit{something }&={\color{red}{ \textit{some value }}}&\textit{something else}\\ \quad \\
y&={\color{red}{ n}}&x&\implies y={\color{red}{ n}}x
\end{array}\\ \quad \\

c=({\color{red}{ n}})t\quad
\begin{array}{ccllll}
text(t)&cost(c)\\
\hline\\
5&2\\
10&4
\end{array}\implies t=5\qquad c=2\implies 2=({\color{red}{ n}})5\)

solve for "n" to find the "constant of variation"

once you find that, plug it in the original equation

to know how much Cost(c) is when Text(t) is 4, well, in the equation just set t=4

Answer 4

johnlegend, no worries ^_^ you had the right idea!
just plug in 10 rather than 5
so 10/10 = 1 which is not 4
so A and B will Not work

Answer 5

@jigglypuff314

Answer 6

yes! so that one works! :D

Answer 7

@jigglypuff314 and @jdoe0001 thanks you both were a great help! :D

Answer 8

Glad we could help :)