Elementary school grade 6 mathematics volume 1 fraction mixed operation A batch of 80 tons of goods can be transported by one truck at 15:00 and by one truck at 40 hours. How many hours can be transported by two trucks at the same time

Elementary school grade 6 mathematics volume 1 fraction mixed operation A batch of 80 tons of goods can be transported by one truck at 15:00 and by one truck at 40 hours. How many hours can be transported by two trucks at the same time

Method 1
80÷(80÷15+80÷40)
=80÷(16/3+2)
=80÷22/3
=120 / 11 hours
Method 2
1÷(1÷15+1÷40)
=1÷(1/15+1/40)
=1÷11/120
=120 / 11 hours