help!!
At a high school, the average grade for the English 10 provincial is 64, with a standard deviation of 10. If 20 students scored between 73 and 86 on the exam, how many students took the exam? Use z scores in your solution

Question

help!!
At a high school, the average grade for the English 10 provincial is 64, with a standard deviation of 10. If 20 students scored between 73 and 86 on the exam, how many students took the exam? Use z scores in your solution

anonymous · Answer

ok 
lets solve this 
$$\Large P(73<X<86)$$
$$\Large Z=\frac{x-u}{\sigma}$$
so
$$\Large  (\frac{73-64}{10})<Z<(\frac{86-64}{10})$$

so we have
$$\Large (0.9<Z<2.2<)$$

can you do this using table ?

anonymous · Answer

@Murry  can you find above?

anonymous · Answer

and it is 
$$\Large (0.9<z<2.2)$$

anonymous · Answer

@Murry your ans is 118 ?
can you confirm this ?

anonymous · Answer

How do I find the above? Do i look at the z-score table?

anonymous · Answer

yes   first find for z=2.2
  then find z=0.9
subtract the two values

anonymous · Answer

your answer is 118?

anonymous · Answer

thank you !

anonymous · Answer

did you get it ?

anonymous · Answer

i think so

anonymous · Answer

can you show me your work  how did you get it ?

anonymous · Answer

it shows that the z score should be .9890 ...?

anonymous · Answer

yes for z=2.2 it is u got it
now for 
z=0.9

anonymous · Answer

.8389 ?

anonymous · Answer

little bit different i found z=0.8159

anonymous · Answer

ok now subtract two values
0.9890-0.8159=0.1731     it means 17.3 % of the 20 are getting no between 73 and 86

so divide 20 by 0.1731
20/0.1731=115.5  =116 students

anonymous · Answer

Thank you, your a life saver

anonymous · Answer

you 're welcome :)