Divisor is equal to zero

Hi,

WISH YOU ALL A VERY HAPPY NEW YR. To find the buffer hit ratio, when I executed the following query its giving me one error "
(a.value+b.value))

     *
ERROR at line 4:
ORA-01476: divisor is equal to zero
"

The query is :
"column "logical_reads" format 99,999,999,999
column "phys_reads" format 999,999,999
column "phy_writes" format 999,999,999
select a.value + b.value "logical_reads", c.value "phys_reads",
round(100 * ((a.value+b.value)-c.value) / (a.value+b.value))
"BUFFER HIT RATIO"

from v$sysstat a, v$sysstat b, v$sysstat c where
a.statistic# = 38
and
b.statistic# = 39
and
c.statistic# = 40;"

????????

--
Thanks & Regards,
T. Onkar Nath
OneAPPS Enterprise Technology Pvt. Ltd.
       to_onkar_at_yahoo.com
       onkarnath.tiwary_at_gmail.com