2) How much PURE copper must be added to 50.255kg of an allow containing 12% copper to raise the copper content to 21%

let x=amt of pure copper to add:

12%*50+100%x=21%(50+x)

6+x=10.5+.21x

.79x=4.5

x=5.7

amt of pure copper to add: 5.7 kg

Step-by-step explanation:

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answer

a,b, and d

explanation

a reflection angle is more than

but less than;

an angle that measures

is a reflex angle.(true)

an angle that measures less than

is acute.(true)

provided we are considering angles greater or equal to zero.

an acute angle lies in the range.

an obtuse angle is less than 180° but more than 90°

an angle that measures 300° is obtuse (false)

an angle that measures 65° is an acute angle.(true)