High School

A store had 175 cell phones in the month of January. Every month, 10% of the cell phones were sold, and 10 new cell phones were stocked in the store.

Which recursive function best represents the number of cell phones in the store \( f(n) \) after \( n \) months?

A. \( f(n) = 175 − 0.9 \times f(n − 1) + 10, \, f(0) = 175, \, n > 0 \)

B. \( f(n) = 0.1 \times f(n − 1) + 10, \, f(0) = 175, \, n > 0 \)

C. \( f(n) = 175 + 0.9 \times f(n − 1) + 10, \, f(0) = 175, \, n > 0 \)

D. \( f(n) = 0.9 \times f(n − 1) + 10, \, f(0) = 175, \, n > 0 \)

Answer :

Answer: f(n) = 0.9 × f(n − 1) + 10, f(0) = 175, n > 0


Step-by-step explanation:

Given: A store had 175 cell phones in the month of January.

Every month, 10% of the cell phones were sold and 10 new cell phones were stocked in the store.

Let n be the number of months

Then when n=0

f(0)=175

After first month , n=1

The number of cell phone in store=[tex]175-10\%\ of\ 175+10[/tex]

Thus [tex]f(1)=f(0)-10\%\ of\ f(0)+10[/tex]

[tex]=f(0)-0.1\timesf(0)+10\\=f(0)(1-0.1)+10\\=f(0)(0.9)+10\\[/tex]

Similarly we can do till n months, we get

f(n)=0.9×f(n−1)+10, f(0) = 175, n > 0

Answer:

[tex]f(n)=0.9\times f(n-1)+10, f(0) = 175, n > 0[/tex]

Step-by-step explanation:

Given :

A store had 175 cell phones in the month of January.

Every month, 10% of the cell phones were sold and 10 new cell phones were stocked in the store.

To Find:

Which recursive function best represents the number of cell phones in the store f(n) after n months?

Solution:

Let n be the number of months

So, when n=0

f(0)=175

Now, after 1 month i.e. At n=1

Now we are given that Every month, 10% of the cell phones were sold and 10 new cell phones were stocked in the store.

The number of cell phone in store after 1 month =

[tex]175-10\%\ of\ 175+10[/tex]

Thus [tex]f(1)=f(0)-10\%\ of\ f(0)+10[/tex]

[tex]f(1)=f(0)-0.1\times f(0)+10[/tex]

[tex]f(1) =f(0)(1-0.1)+10[/tex]

[tex]f(1) =f(0)(0.9)+10[/tex]

Similarly we can do till n months,Thus , we get

[tex]f(n)=0.9\times f(n-1)+10, f(0) = 175, n > 0[/tex]

Hence Option 4 is correct.