Question

Anneliese sent 9 emails on Monday, 13 emails on Wednesday, 15 emails on Thursday, and 17 emails on Friday. Based on the trend, how many emails did Anneliese send on Tuesday?

Answer 1

9 = monday
?=tuesday
13=wednesday
15=thursday
17=friday
 everyday she sends 2 more emails than the previous day so Tuesday she sent 11 emails
she starts the week with 
9 (mon)
9+2=11 (tues)
11+2=13 (weds)
13+2=15(thurs)
15+2=17(fri)
HOPE THIS HELPS

Answer 2

Let's make a table of the days, and the number of mails sent each day:

          Day                   nr of mails sent

       Monday                        9
       Tuesday                       ?      
       Wednesday                 13
       Thursday                     15
       Friday                          17

In the last 3 days, the number of mails increased each day by 2, so we could make the assumption that on Tuesday, there were 2 mails less sent than on Wednesday.

So, on Tuesday, we assume that 13-2=11 mails were sent. 

We check this assumption with the number of mails sent on Monday, and it works again. So, our assumption is correct.


Answer: 11