Question

Question 6 (ii)
A teacher wanted to analyze the performance of two sections of students in a mathematics test of 100 marks. Looking at their performances, she found that a few Students got under 20 marks and a few got 70 marks or above.So she decided to Group them into intervals of varying sizes as follows : 0−20,20−30…60−70,70 − 100. Then she formed the following table:
$\begin{array}{cc}\text{Marks}& \text{Number of student}\\ 0-20& 7\\ 20-30& 10\\ 30-40& 10\\ 40-50& 20\\ 50-60& 20\\ 60-70& 15\\ 70-above& 8\\ \text{Total}& 90\end{array}$
(ii) Find the probability that a student obtained marks 60 or above.

Answer 1

Total number of students = 90
(ii) Number of students obtaining marks 60 or above = 15+8 = 23
Hence, required probability, $P=\frac{23}{90}$