Question

After reading 80% of her e-mails in her inbox, Danette still has M 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: (Choice A) 5M (Choice B) 1.8M (Choice C) 80M (Choice D) 0.8 M ​ (Choice E) 1−0.8 M ​

Answer 1

Answer:

(Choice A) 5M

Step-by-step explanation:

Let total no. of e-mails in inbox be x

Since she read 80 % of mails i.e 80 % of x

⇒$80\% \times x$

⇒$\frac{80}{100}\times x$

⇒$0.8 x$

So, she read 0.8x e-mails.

So, remaining email = total e-mails - read e-mails

                                  $=x-0.8x$

Since we are given that Danette still has M unread e-mails.

⇒ $M=x-0.8x$

⇒ $M=x(1-0.8)$

⇒ $M=x\times 0.2$

⇒ $\frac{M}{0.2}=x$

⇒ $\frac{10M}{2}=x$

⇒ $5M=x$

Thus the expression  represent the number of e-mails Danette had in her inbox before she started reading is 5M.

Hence Choice A is correct.