To find it directly
A = 2 pi r h
A is proportional to rh
factor 2
A is multiplied by 2 * 2 = 4
factor 3
3 * 3 =9
factor 5
5 * 5 = 25
factor 10
10 * 10 = 100
(b) the increase in A by factor x is x^2
c(20)^2 = 400
Answer: 1/70
Step-by-step explanation:
This is a question that can also be interpreted as what is the probability of having the first number of a phone number to be 8 and the last number of the phone number to also be 8. This answer gives the fraction of the phone numbers that starts with 8 and end with 8.
Since three numbers (0,1,2) cannot start a phone number and we are left to pick from 7 numbers,
then the probability of figure "8" starting phone number = 1/7
Since all 10 numbers can possibly end a phone number,
then the probability of having figure "8" as the last digit of a phone number = 1/10
Hence probability of having "8" as the first and last digit of a phone number = fraction of total telephone numbers that begin with digit 8 and end with digit 8 = 1/7 × 1/10 = 1/70.
Answer:

Step-by-step explanation:
1) Use square sum: (a + b)² = a² + 2ab + b².

<u>Therefor</u><u>,</u><u> </u><u>the</u><u> </u><u>answer</u><u> </u><u>is</u><u> </u><u>x</u><u>²</u><u> </u><u>+</u><u> </u><u>2xy</u><u> </u><u>+</u><u> </u><u>y</u><u>²</u>.
A reasonable number between 18 and 23 is 20. 69 minutes is 3 times 23 minutes, so we multiply the 20 by 3, getting an estimate of 60 cars.