Answer:
about 15 hours
Step-by-step explanation:
You want to find t such that N(t)=200. Fill in the equation with that information and solve for t.
200 = 400/(1 +399e^(-0.4t))
1 +399e^(-0.4t) = 400/200 = 2 . . . . . multiply by (1+399e^(-0.4t))/200
399e^(-0.4t) = 1 . . . . . . . . . . . . . . . . . . subtract 1
e^(-0.4t) = 1/399 . . . . . . . . . . . . . . . . . .divide by 399
-0.4t = ln(1/399) . . . . . . . take the natural log
t = ln(399)/0.4 ≈ 14.972 . . . . . . . divide by -0.4, simplify
Rounded to tenths, it will take 15.0 hours for half the people to have heard the rumor.
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Answer:
a. 5cm
Step-by-step explanation:
r. m+m+n+n= 34
t. m+n+n+1=30
r. 2m + 2n =34
t. m + 2n + 1 = 30
after multiple by negative t row
t. -m -2n -1 = -30
and combine the 2 rows
2m -m +2n - 2n -1 = 34 - 30
m - 1 = 4
and we add one to each side of the operation
m - 1 + 1 = 4 + 1
m = 5