Chapter 7
The Mathematics of Maybe: Introduction to Probability
CBSE Class 9
Mathematics Solutions
Educart Mathematics class Class 9 NCERT Exemplar cover
Question:

A tyre company records distances before replacement in 1000 cases.

Distance (km)Number of cases
Less than 400020
4001 to 9000210
9001 to 14000325
More than 14000445

Find the probability that a randomly chosen tyre lasts:

(A) Less than 4000 km.

(B) Between 4000 and 14000 km.

(C) More than 14000 km.

Answer: Verified

Total cases = 20 + 210 + 325 + 445 = 1000

(A) P(less than 4000 km)=201000=150P(\text{less than } 4000 \text{ km}) = \frac{20}{1000} = \frac{1}{50}

(B) P(between 4000 and 14000 km)

=210+3251000= \frac{210 + 325}{1000}

=5351000=107200= \frac{535}{1000} = \frac{107}{200}

(C) P(more than 14000 km)=4451000=89200P(\text{more than } 14000 \text{ km}) = \frac{445}{1000} = \frac{89}{200}

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