Answer:
10
Step-by-step explanation:
Let c = sum of ages of all children.
mean age of all children = c/15 = 7
c = 15 * 7 = 105
The sum of the ages of all children is 105.
Let b = sum of ages of the 9 boys.
mean age of boys = b/9 = 5
b = 9 * 5 = 45
The sum of the ages of the boys is 45.
The sum of the ages of the girls is c - b.
c - b = 105 - 45 = 60
The number of girls is 15 - 9 = 6
mean age of girls = (sum of ages of the girls)/(number of girls) =
= 60/6 = 10
For this case we have the following function:
n (t) = 2400 * (5) ^ t
For n (t) = 60000 we have:
60000 = 2400 * (5) ^ t
We clear the value of t.
For this we use the logarithm:
(5) ^ t = 60000/2400
log5 ((5) ^ t) = log5 (60000/2400)
t = log5 (60000/2400)
t = 2 days
Answer:
the number of bacteria in the culture will be 60 comma 000 after:
t = 2 days
The surface area will be 456.2 to the second power
Answer:
Step-by-step explanation:
The perimeter is obtained by taking the sun of the fence :
Outer fencing :
Let's obtain b :
From Pythagoras :
b² = 15² - 12²
b = sqrt(225 - 144)
b = 9
Outer fencing = 2(12+6) + 2(8+9)
= 2(18) + 2(17)
= 36 + 34
= 70
Inner fencing :
(8 + 9 + 12 + 6 + 15 + 10) = 60
(70 + 60) = 130 yards
