Answer:
# of 20cent stamps = 8
Step-by-step explanation:
Let the number 20cent stamps be = x
Let the number 60 cents stamps be = y
Total number of stamps => 20 = x + y ----------- ( 1 )
Total cost of the stamps = 8.80
That is, 0.20x + 0.60y = 8.80 ------------- ( 2 )
( 2 ) => 20x + 60y = 880
=> x + 3y = 44
=> x = 44 - 3y
Substitute x in ( 1 ) => x + y = 20
44 - 3y + y = 20
- 2y = 20 - 44
- 2y = - 24
2y = 24
y = 12
Substitute y = 12 in ( 1 ) => x + y = 20
x + 12 = 20
x = 8
Answer:
Coal is formed of carbon.
(a) Length of the height is 2.732 m
(b) Length of the base is 5.466 m
<u>Explanation:</u>
An image is attached for reference.
(a)
In ΔAOB,

In ΔBGD,

According to the figure, BG = OE = 1.732 m
Height of the tent, AE = AO + OE
= 1 m + 1.732 m
= 2.732 m
(b)
DF = ?
In ΔAOB,

According to the figure, OB = GE = 1.733 m
In ΔBGD,

According to the figure, DE = DG + GE
DE = 1 m + 1.733 m
DE = 2.733 m
Length of the base, DF = 2 X DE
DF = 2 X 2.733 m
DF = 5.466 m
Initial volume of water = 20 litres
Final volume of water = 14 litres
Leaked volume of water = 6 litres
Time taken to leak the water = 24 hours
Leaked volume in an hour = 6 / 24
= 0.25 litres