Its 81 centimeters because you round 5 and over. So nearest centimeter means 2 whole numbers which is 81
You should first find out what lines are what,
Like for example, If you had 5 - 10 - 15 as the Y Lines and the bar was between 5 and 10 then your best bet would be to estimate what the middle of 5 and 10 is which would be 7 or 8.
Answer:
Mean = 0.2(100) = 20
Variance = 0.2×0.8×100 = 16
Standard deviation = 4
Yes, np > 5 & nq > 5
Y-y(1) = m(x - x(1))
y - 1 = (-3/4)(x + 8)