Answer:
2.1 m
Step-by-step explanation:
The gutter is in the shape of a cylinder.
Its volume is 20 liters and its diameter is 11 cm (0.11 m).
Its radius is half of its diameter => r = 0.055 m.
The volume in cubic metres:
1 litre = 0.001 cubic metres
20 litres = 20 * 0.001 = 0.02 cubic metres
The volume of a section of guttering is given as:

where h = length of the guttering
Therefore:

The length of the section of guttering is 2.1 m long.
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-2(m+1)=10
Distributive property
-2m + -2 = 10
Elimination way
-2m + -2 + 2 = 10 + 2
-2m = 12
-2m/-2 = 12/-2
m = -6
Depends whether it’s compound or simple interest