For i=1 ===> Sum=4
for i=2===> Sum=2
for I=3===> Sum=1
Hence the answer is 7
Or you could have use the Sum formula of a GP:
Sum = a(1-r)^n/(1-r), with a=1, r=1/2 & n=3
Remark
Writing down the givens for these questions is almost a command. You must know which equation of the big 4 to use. The givens + what you want to find will determine the equation.
Givens
vi = 30.7 km/hr = 30.7 km/hr *[1000m/1km]*[1hr/3600sec] = 8.52m/sec
vf = 120 km/hr = 120 km/hr * [1000 m/1 km]*[1h/3600 sec] = 33.3 m/s
t = 4.9 seconds
d = ???
Formula
d = (vi + vf)*t/2
Solve
d = ( 33.3+8.52 )*4.9/2
d = (41.85333)*4.9/2
d = 205.02/2
d = 102.51 m<<<Answer
Answer:
Step-by-step explanation:
x ≥ 2800
12*75=900
900< x
Kingston Edmonds
It’s longer, also I think I did this before
