MHB Aux24 probability student range

[karush]

The frequency chart below shows the cumulative number of Ms. Hernandez's science students
whose test scores fell within certain score ranges All test scores are whole numbers.
Cumulative number Score range of students

$\begin{array}{lll}
&65-70& 12\\
&65-80& 13\\
&65-90& 19\\
&65-100& 21
\end{array}$
a.1 b.6 c.8 d.12 e.13
How many students have a test score in the interval 71-80

ok I guessed this to be 13 but ?
what about students who in the 65-71 range
I don't know of any equation to figure this other than just observation

 

[skeeter]

12 students scored in the range 65 to 70
13 students scored in the range 65 to 80

wouldn't that mean only 1 student scored in the range 71 to 80 ?

 

[karush]

sorry i don't get it

 

[skeeter]

call it a "linear" Venn diagram ...

 

[karush]

That helps

 

[HOI]

Why would you read "13 students have grades in the range of 65 to 80" and conclude that "13 students have grades in the range 71 to 80"? 65 is NOT 71!

13 students have grades in the range 65 to 80 but 12 of those have grades in range 65 to 70.