There are 9 mathematics books 8 physics books and some chemistry books on a shelf. The probability of selecting a chemistry book from the shelf is equal to 7 times the difference of probabilities of selecting a mathematics book and a physics book from the shelf. Find the number of chemistry books on the shelf
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Answers
Step-by-step explanation:
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Answer:
There are 7 chemistry books on the shelf.
Step-by-step explanation:
No. of Mathematics books = 9
No. of Physics books = 8
Let the no. of Chemistry books = x
Total no. of books = 9+8+x
= 17+x
Probability of selecting a chemistry book from the shelf is equal to 7 times the difference of the probabilities of selecting a mathematics book and a physics book from the shelf.
=> P(che book) = 7* [P(maths book) - P(phy book)]
now,
Probability(event) = No. of favorable outcomes / total no. of outcomes.
=>
P(che. book) = no. of Chemistry books / total no. of books
= x/17+x
P(mat. book) = no. of Maths books / total no. of books
= 9/17+x
P(phy. book) = no. of Physics books / total no. of books
= 8/17+x
P(che book) = 7* [P(maths book) - P(phy book)]
= x/17+x = 7* [(9/17+x) - (8/17+x)]
= x/17+x = 7* (1/17+x)
= x/17+x = 7/17+x
= x = 7
=> No. of Chemistry books on the shelf = x = 7
hope it helped :)