Melanie had 255 dollars to spend on 8 books. After buying them she had 15 dollars. How much did each book cost?
2 answers:
1. She starts with $255.
2. She purchases 8 books for an unknown cost per book, so she spends 8 * (unknown cost per book).
3. She is left with $15.
Let's set up an equation:
Now, we solve. First, we'll subtract 255 from each side:
Now, we'll divide through by -8:
The cost per book is $30. Let's check it out:
$30/book * 8 books = $240
She started with $255 and spent $240, which leaves her with $15. Exactly what the original question indicated. We're done. (Those are some expensive books.)
2. She purchases 8 books for an unknown cost per book, so she spends 8 * (unknown cost per book).
3. She is left with $15.
Let's set up an equation:
Now, we solve. First, we'll subtract 255 from each side:
Now, we'll divide through by -8:
The cost per book is $30. Let's check it out:
$30/book * 8 books = $240
She started with $255 and spent $240, which leaves her with $15. Exactly what the original question indicated. We're done. (Those are some expensive books.)
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Answer:
Probability that detector B goes off is '0.615'
Step-by-step explanation:
Given that:
1) Probability that detector A goes off and detector B does not go off is 0.25.
2)Probability that detector A does not go off is 0.35.
3)Probability that detector A goes off is (1-0.35)=0.65
Assuming that
Probability that detector B goes off is 'p' Hence the probability that detector B does not goes off is (1-p)
Thus the probability that detector A goes off and detector B does not go off is product of the individual probabilities
Probability that detector B goes off is '0.615'