The area equation is 
, which when solved equals 50.24. That's the third answer on your list.
Who kno the answer ? Please help
2 answers:
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Remember the divisibility rule for 9. The sum of the digits of the number must be divisible by nine.
Let the digit be
. Then 
has to be divisible by nine. Recalling that 
, we note that 
.
Let the digit be