After reading 80\%80% of her e-mails in her inbox, Danette still has MM unread e-mails.
Which of the following expressions could represent the number of e-mails Danette had in her inbox before she started reading?
Choose 2 answers:
Choose 2 answers:

(Choice A)
A
\dfrac{M}{1-0.8}
1−0.8
M


(Choice B)
B
5M5M

(Choice C)
C
\dfrac{M}{0.8}
0.8
M


(Choice D)
D
1.8M1.8M

(Choice E)
E
80M80M

Respuesta :

Answer:   The correct options are.....

A)   [tex]\frac{M}{1-0.8}[/tex]   and

B)   [tex]5M[/tex]

Step-by-step explanation:

Suppose, the number of e-mails Danette had in her inbox before she started reading was [tex]X[/tex].

Percentage of read emails is 80%, so the number of read emails [tex]= (\frac{80}{100}*X)=0.8X[/tex]

Thus, the number of unread emails [tex]= X-0.8X=X(1-0.8)[/tex], which is given as [tex]M[/tex].

So, the equation will be........

[tex]X(1-0.8)=M\\ \\ \Rightarrow X=\frac{M}{1-0.8} (Answer: 1) \\ \\ \Rightarrow X=\frac{M}{0.2}\\ \\ \Rightarrow X=(\frac{1}{0.2})M=5M (Answer: 2)[/tex]

Thus, the expressions which could represent the number of e-mails Danette had in her inbox before she started reading are:  [tex]\frac{M}{1-0.8}[/tex] or [tex]5M[/tex]