maths urgent
posted by joel .
The average mass of half the number of crabs in a basket is 350g, the average mass of the remaining crabs is 300g. If the total mass iof the crabs in the basket is 13kg, how many crabs are there in the basket?

350+300=650g
13kg=13000g
13000/650
=20crabs 
let number of crabs be x
mass of 1/2 the craps
= 350(x/2) =175x
mass of remaining ones = 300(x/2) = 150x
175x + 150 = 13000
325x = 13000
x = 40
there were 40 crabs
check:
half of 40 = 20
so 20(350) + 20(300) = 13000
oi's answer makes no sense and does not check out.
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