Question

Marika is training for a track race. She starts by sprinting 100 yards. She gradually increases her distance, adding 4 yards a day for 21 days. Which explicit formula models this situation? A. an = 100 + (n – 1)21 B. an = 21 + (n – 1)4 C. an = 100 + (n – 1)4 D. an = 4 + (n – 1)100

Answer 1

I think it's C

Explanation:

I'm not 100% sure but thats what i would guess.

Answer 2

C.
`a_n = 100 + (n - 1)4`

Explanation:

Given,

Initial distance Marika covered = 100 yards,

Also, She gradually increases her distance by 4 yards,

Thus, the difference between the distance of consecutive days is 4 yards,

So, there is an AP that shows the given situation,

Having first term, a = 100,

Common difference, d = 4,

Since, the explicit formula of an AP is,

`a_n=a+(n-1)d`

`\implies a_n=100+(n-1)4`

Which is the required formula.

Option 'C' is correct.