In a food factory, machine A can produce 40 muffins in 5 minutes while machine B can produce 25 more muffins in the 5 minutes. If the two machines are operating together, how much time will they take to produce 840 muffins?

min

The rate for machine A: 40 ÷ 5 = 8

The rate for machine B: (40 + 25) ÷ 5 = 13

Then, the total rate for them: 8 + 13 = 21

Thus, the time needed: 840 ÷ 21 = 40 min