Answer:
7 minutes
Step-by-step explanation:
1000 stairs in 25 minutes
280 stairs in 280*25 / 1000 = 7 minutes
Let
be the amount of the 30% alloy and
the amount of the 60% alloy the metalworker will use. However much is used, the final alloy will have a mass of

kilograms. For each kg of the 30% alloy used, 0.3 kg is copper; similary, each kg of the 60% alloy contributes 0.6 kg, so that

Now,






Answer:
No
Step-by-step explanation:
It is a solution to the first equation, but not the second equation.
Answer:
step 6 has an algebraic error