Answer:
50% of all students scored more than 48 marks.
Step-by-step explanation:
1) The baseline of the box, in a box plot is the first quartile, the line in the middle is the median or Q2 and the last line (or top line) is the third quartile. Namely,
[tex]Q_{1}=30, Q_{2}=48 \:and\:Q_{3}=70[/tex]
2) The Question says "nobody took 30, 48 or 70 as their grades. But 120 students gained less than 70", i.e. 120 are within the 75% of the sample.
3) If [tex]Q_{2}=48[/tex] then 50% of the students scored more than 48. And 50% of the students scored less than 48. That is also known as the Median.
So 50%, the half of all students scored more than 48 marks.
50% of the total number of students gained more than 48 marks.
Given information:
The box plot shows information about the marks scored in a test. The three quartiles are 30, 48, and 70.
Quartile 1 is of 30 marks, Q2 is of 48 marks and Q3 is of 70 marks.
Now, the middle quartile Q2 or 48 is the median of the data.
Now, it is given that nobody gained 30, 48 or, 70 marks and 120 students gained less than 70 marks.
120 students have scored less than 70 marks or under the 1st and 2nd quartile.
Now, according to the 2nd quartile, 50% of the students (total) will score more than 48 marks, and 50% will score less than 48 marks.
Therefore, 50% of the total students gained more than 48 marks.
For more details, refer to the link:
https://brainly.com/question/16983321
