For this case we can make the following rule of three:
1/10 scarf ------> 4/5 hour
x ------------------> 1 hour
Clearing the value of x we have:
x = (1 / (4/5)) * (1/10)
Rewriting we have:
x = (5/4) * (1/10)
x = 5/40
x = 1/8
Answer:
A fraction of a scarf that alison can knit in 1 hour is:
x = 1/8
Just change feet into yards and multiply it
This is a geometric sequence with first term 1 and common ratio -1/2. r=-1/2.
a(n) = a(1)*(r)^(n-1).
Check: If n=2 our formula must return -1/2. Does it?
a(2) = 1(-1/2)^(2-1) = (-1/2)^1 = - 1/2. Yes.
a(3) should be 1/4. Is it? a(3) = (-1/2)^(3-1) = 1/4 Yes.
Then a(8) = (-1/2)^(8-1) = (-1/2)^7 = -1 / 2^7 = -1/128 (answer)
