12+12+9+9= 42
12 x 9= 108
12^2 x 9^2 =6561
( I hope I did that right for you )
Answer:
7.8 cm and 25.3 cm
Step-by-step explanation:
Using Pythagoras' identity in the right triangle.
The square on the hypotenuse is equal to the sum of the squares on the other 2 sides, that is
?² + 7² = 10.5²
?² + 49 = 110.25 ( subtract 49 from both sides )
?² = 61.25 ( take the square root of both sides )
? = 
≈ 7.8 cm ( to 1 dec. place )
Then
P = 10.5 + 7 + 7.8 = 25.3 cm
Answer:
About 113,097.34 units
Step-by-step explanation:
The volume of a sphere can be found with the equation V = 
πr³ when r is the radius.
V = πr³
V = π(30)³
V ≈ 113,097.34 units
Answer: the speed of the current is 9 mph.
Step-by-step explanation:
Let x represent the speed of the current.
A boat can travel 21 mph in still water. If it travels 270 miles with the current. It means that the total speed with which the boat travelled with the current is (21 + x) mph.
Time = distance/speed
Time spent by the boat in travelling 270 miles is
270/(21 + x)
In the same length of time, it travels 108 miles against the current. It means that the total speed with which the boat travelled against the current is (21 - x) mph.
Time = distance/speed
Time spent by the boat in travelling 108 miles is
108/(21 - x)
Since the time is the same, then
270/(21 + x) = 108/(21 - x)
270(21 - x) = 108(21 + x)
5670 - 270x = 2268 - 108x
108x + 270x = 5670 - 2268
378x = 3402
x = 3402/378
x = 9
