189 because 20.7 rounds to 21 and 9.18 rounds to 9
21 * 9 = 189
The surface area is 1000 and the volume is 49
Answer:
The number of duck is 32.
Step-by-step explanation:
Let x represent the number of rabbits.
Let y represent the number of ducks
From the question given:
The sum of rabbit and duck is 36 i.e
x + y = 36 .... (1)
The sum of the feets of the rabbit and duck is 80.
Rabbits has 4 legs
Duck has 2 legs
Therefore, the sum their feets (i.e 80) can be written as:
4x + 2y = 80 .... (2)
The equations are:
x + y = 36 .... (1)
4x + 2y = 80 .... (2)
Solving by substitution method:
From equation (1)
x + y = 36
Make x the subject
x + y = 36
x = 36 - y
Substitute the value of x into equation (2)
4x + 2y = 80
x = 36 - y
4(36 - y) + 2y = 80
Clear bracket
144 - 4y + 2y = 80
144 - 2y = 80
Collect like terms
- 2y = 80 - 144
- 2y = - 64
Divide both side by - 2
y = - 64/ - 2
y = 32
Therefore, the number of duck is 32.
