machine manufactures at the rate of 20 cans per hr
In 2 hr machine m/f 40 cans

3 boxes = 30 cans.
There are total 40 cans to be packed

rate of maria = 30 cans per hr.

For 40 cans total time taken by maria = \(\frac{40}{30}\) hr = 80 mins
_________________

We just have to calculate Maria's rate of packing one box. That's 20 minutes.
So for 4 boxes in 2 hours (40 cans), it'll take 20*4=80.

Total cans in 2 hours 20 * 2 = 40

10 can / 1 Box = 40 can / B box
B box = 4 box

Now, 3 box / hour
so, 60 / 3 = M / 4
M = 80

Total can manufactured 20 X 2 equal 40
Total box 40/10 equal 4
Time required 1/3 * 4*60 equal 80 min.

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