Answer: A
Step-by-step explanation: 3(1)+k =8 8-3=5
R = speed in still water
r + c = speed with current
r - c = speed against current
3.5(r + c) = 70
r + c = 20
c = 20 - r
4(r + c) = distance from pier to pier
5(r - c) = distance from pier to pier
4(r + c) = 5(r - c)
4(r + 20 - r) = 5(r - 20 + r)
80 = 10r - 100
180 = 10r
18 = r
The speed in still water is 18 km/hour
Let's see what to do...
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Step (1)
Look : 16 , 10 , 4 , ...
It is an arithmetic sequence.
So first we have to find the value of the ratio(( d )) .
To do this, we need to subtract each sentence minus the previous sentence.
So we have : 10 - 16 = - 6
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Step (2)
To find the nth sentence in an arithmetic sequence, we must use the following equation :

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Step (3)
To find the 6th term just need to put the following parameters in the above sequence.
t(1) = 16 ------ n = 6 ------ d = -6





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And we're done.
Thanks for watching buddy good luck.
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