Hanna has twice as many erasers as Rachel.  Rachel has three less than one-half as many erasers as Tanya has red erasers.  If Tanya has 20 erasers, and half of them are red, how many erasers does Hanna have?
Half of Tanya's 20 erasers are red, so she has 20/2=<<20/2=10>>10 red erasers.
One-half as many erasers as Tanya has red erasers is 10/2=<<10/2=5>>5 red erasers.
Rachel's three less than one-half as many erasers as Tanya's red erasers, which is 5-3=2 erasers.
Hanna has twice as many erasers as Rachel, for a total of 2*2=<<2*2=4>>4 erasers.
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