Her cake is half ...

1. Her cake is half as big as mine. Which one of us has the bigger/biggest cake? Me or her?
("bigger" is formally correct when comparing two, but in everyday English you would often hear "biggest".)

2. There are 500 biology books, but half as many math books. Are there more biology books than maths books?

If someone says " There're 500 biology book , but there're half as many maths books.
Does he or she mean that maths book more than biology book?

If you have half as much A as B, then you have twice as much/many B as A.
If you have half as much/many again A as B, then you have one and a half times as much/many A as B.

AnonymousIf someone says " There're 500 biology book , but there're half as many maths books.Does he or she mean that maths book more than biology book?

Sorry if I misunderstood the post. I thought you were asking how to write the sentences, not literally asking for the answers to the questions.

AnonymousIt's so confusing .

half as many ~ x 1/2
twice as many ~ x 2

Suppose I have 6 chairs. Jack has 3 chairs. Joan has 12 chairs.

6 x 1/2 = 3. Jack has half as many chairs (3) as I do (6).
6 x 2 = 12. Joan has twice as many chairs (12) as I do (6).

CJ

If I want to say " Her cake is half as big as mine" means .my cake is bigger that hers. Is that correct?
And is it okay to use " third" ,quarter, fifth ...depending on what I want to say?
e.g " Her cake is fifth as big as mine." Means my cake is bigger than hers? Is that correct?

Anonymous" Her cake is half as big as mine" means .my cake is bigger that hers.

Right.

AnonymousHer cake is a fifth as big as mine." Means my cake is bigger than hers?

Right. With "half" you don't need "a". With the others you need "a".

Anonymousis it okay

Okay,
Thank you very much.??