6e+2f-21g that the answers if I'm not wrong
To simplify 7C4 we use the combination formula given by:
nCr=n!/[(n-r)!r!]
thus:
In our case we shall have:
n=7 and r=4
7C4
=7!/[(7-4)!4!]
=5040/[6×24]
=5040/144
=35
The answer is 35
We are given that:
t = time required for Sprinkler System A
t + 4 = time required for Sprinkler System B
Hence the rates are:
1 / t = rate for Sprinkler System A
1 / (t + 4) = rate for Sprinkler System B
The overall equation is:
1 / t + 1 / (t +
4) = 1 / 1.5
Solving for t by multiplying everything by t*(t + 4):
t + 4 + t = (1 / 1.5) (t) (t + 4)
3 t + 6 = t^2 + 4 t
t^2 + t = 6
Completing the square:
t^2 + t + 0.25 = 6 + 0.25
(t + 0.5)^2 = 6.25
t = -0.5 ± 2.5
t = -3, 2
Since time cannot be negative, therefore:
t = 2 hours
t + 4 = 6 hours
Alone, Sprinkler System A takes 2 hours while Sprinkler
System B takes 6 hours.
Answer:
10
Step-by-step explanation:
sorry if i got it wrong!:(
