On 5 September to 8 September, an average of 44 cookies were sold and from 9th September to 13 September, an average of 27 cookies were sold. $218 worth of cookies were sold from 14 September to 24 September. Given that a cookie was sold for $2, find the average number of cookies sold from 5 September to 24 September.
Number of cookies sold from 14 September to 24 September
= 218 ÷ 2
= 109

Number of days from 5 September to 8 September
= 8 - 5 + 1
= 4

Number of days from 9 September to 13 of September
= 13 - 9 + 1
= 5

Total number of cookies sold
= (4 x 44) + (5 x 27) + 109
= 176 + 135 + 109
= 420

Number of days from 5 September to 24 September
= 24 - 5 + 1
= 20

Average number of cookies sold
= 420 ÷ 20
= 21

Answer(s): 21