Given below is the frequency distribution of marks of 70 students of Class- $9^{t h}$

Marks 30 - 40 40 - 50 50 - 60 60 - 70 70 - 80 80 - 90

Number of Students 12 25 10 8 10 5

If a student is selected at random, then the probability that his marks are less than 70 is

\frac{57}{70}

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\frac{13}{14}

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\frac{11}{14}

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\frac{47}{70}

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Solution

The correct option is C $\frac{11}{14}$
Total number of students = 70
Number of students who obtained marks less than 70 = 12 + 25 + 10 + 8 = 55
$∴ Required Probability = \frac{Number of favourable outcomes}{Total number of outcomes}$
$= \frac{55}{70}$
$= \frac{11}{14}$

Hence, the correct answer is option c.

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Similar questions

Marks:	0−10	10−20	20−30	30−40	40−50	50−60	60−70	70−80	80−90	90−100
Frequency:	3	5	16	12	13	20	5	4	1	1

80

C.I.	0-10	10-20	20-30	30-40	40-50	50-60	60-70	70-80	80-90	90-100
Freq.	3	5	16	12	13	20	5	4	1	1

80

Marks:	0-10	10-20	20-30	30-40	40-50	50-60	60-70	70-80	80-90	90-100
Frequency:	$3$	$5$	$16$	$12$	$13$	$20$	$5$	$4$	$1$	$1$

class interval	30-40	40-50	50-60	60-70	70-80	80-90
mark	1	2	4	5	6	7

Marks	0 - 10	10 - 20	20 - 30	30 - 40	40 - 50	50 - 60	60 - 70	70 - 80	80 - 90	90 - 100
No. of Students	3	5	7	10	12	15	12	6	2	8

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