Explanation:
Let E be the event of drawing a disc from the box of discs numbered from 1 to 90
Two digit numbers from 1 to 90=10,11,12,.....,90
No. of favorable outcomes=81
Total no. of possible outcomes =90
We know that, Probability P(E) =(Total no.of possible outcomes)(No.of favorable outcomes)=9081=109
Therefore, the probability of a two digit numbered disc from the box of discs numbered from 1 to 90=109
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