Volume Problem.....???

Question

Dimensions of a horizontal cylindrical tank are as follows: 3 meters diameter and 10 meters long.
Determine the liquid volume in the tank if it is filled up to a level of 1 meter.

sweet2water, yes it's horizontal...and no, guessing is not good enough

Answer 1

Sketch circle centre O
A and B are points on circumference where AB is horizontal line below O.
AB is water level.
OD is vertical where D lies on AB
OD = 0.5 m
OB = OA = 1.5 m
OD produced meets circumference at E.
In triangle ODB:-
cos DOB = 0.5 / 1.5
Angle DOB = 70.5°
Angle AOB = 141°
Area of sector AOBE
= (141/360) x π x 1.5² m²
= 2.77 m²
Consider triangle ODB:-
1.5² = 0.5² + DB²
DB² = 1.5² - 0.5²
DB² = 2
DB = √2 m
Area of triangle AOB is given by:-
√2 x 0.5 m² = 0.707 m²
Water X section Area is given by:-
2.77 - 0.707 m² = 2.063 m²
Volume of water = 2.063 x 10 m³
Volume of water = 20.63 m³

Answer 2

Horizontal? I'm getting 120.4 m^3, just a wild guess?

EDIT
31.0 m^3 is my second choice

EDIT2
cosB = (3-1)/3 = 2/3

B = arccos(2/3) = 48.19

2B = 96.38 deg

A_1 = (96.38/360)*pi*3^2 = 7.57

A_2 = 2*1/2*2*sqrt(3^2 - 2^2) = 2sqrt(5) = 4.47

A_3 = area of wetted section = 7.57 - 4.47 = 3.10

volume of water = 10*3.10 = 31.0 m^3