is there a way to make the working out clearer, mathematically? also fifty points because I can't read through the working I have been given by the algorithm.

Colin uses a pump to empty the pond. The level goes down by 20 cm in the first 30 minutes.

Solution :

We know that the volume of the prism is given by,

V
o
l
u
m
e
=
(
B
a
s
e
A
r
e
a
)
×
H
e
i
g
h
t
Volume=(BaseArea)×Height

And also

B
a
s
e
A
r
e
a
=
1
2
×
(
1.4
+
0.6
)
×
2
BaseArea=
2
1

×(1.4+0.6)×2

B
a
s
e
A
r
e
a
=
2
m
2
BaseArea=2m
2


Now,

V
o
l
u
m
e
=
2
×
1
=
2
m
3
Volume=2×1=2m
3


Given that the level of pond goes down by 20 cm in the first 30 minutes. Therefore, the volume becomes,

V
o
l
u
m
e
=
2
×
0.8
=
1.6
m
3
Volume=2×0.8=1.6m
3


Now, the rate of emptying the tank is,

=
2
−
1.6
30
=
1
75
m
3
/
m
i
n
=
30
2−1.6

=
75
1

m
3
/min

We also know that,

t
i
m
e
=
v
o
l
u
m
e
r
a
t
e
time=
rate
volume



t
i
m
e
=
2
1
75
=
150
m
i
n
time=
75
1


2

=150min​