Aubrey has a shelf full of books.

Question

• Exactly 1
}3
of the books on the shelf are mysteries.
• Aubrey has read 10 of the mysteries on the shelf.
• The number of mysteries Aubrey has read is greater than 1
}5
of the number of
mysteries on the shelf and less than 1
}4
of the number of mysteries on the shelf.
Which could be the number of books on the shelf?
a 120 b 140 c 147 d 150

Answer 1

Let
x=number of mystery books on the shelf
then
3x = total number of books on the shelf

we are told that
x/5<10<x/4
multiply by 20,
4x<200<5x
which means that
40<x<50
So the number of mystery books can be any number between 41 and 49. In other words, the possible total number of books could be three times the above numbers, 123, 126, 129,....
Choose the one that suits your answer choices.

Answer 2

I it