lets consider
total number of packages = N
set of all package weights = W
How many packages weight more than 420 grams?
lets check the statement 1 : average ( arithmetic mean) weight per package is equal to weight of lightest package
average weight = A
weight of lightest package = L [weight of any package >= L]
as per statement , A = L
sum of all weights / number of package = L
sum of all weights / N = L
sum of all weights = L*N
if we have set of weights which are not equal then sum of weights will be greater than N*L
example : Weights = { 10, 10, 20}
L = 10, sum = 40, N = 3
A = 40/3 = 13.33
A is not equal to L
A=L only if every single package weighs exactly the same as lightest one.
we can have L = 400 or 500..., we cant find the answer
Since answer could be anything,
statement 1 is not sufficientnow lets check statement 2 - median weight of all packages in depot is 410 grams.
This tells us that exactly half of packages weigh 410 gms or less and exactly half more than 410 gms.
since number of packages weighing more than 420 grams can be different,
statement 2 is not sufficientnow lets consider both statement 1 and statement 2
weight of all packages = median = 410 grams
since 410 is less than 420, answer is definitively 0 packages
therefor, statement 1 and statement 2 combined are sufficient