On 1 June to 4 June, an average of 52 grapefruits were sold and from 5th June to 9 June, an average of 22 grapefruits were sold. $328 worth of grapefruits were sold from 10 June to 20 June. Given that a grapefruit was sold for $4, find the average number of grapefruits sold from 1 June to 20 June.
Number of grapefruits sold from 10 June to 20 June
= 328 ÷ 4
= 82

Number of days from 1 June to 4 June
= 4 - 1 + 1
= 4

Number of days from 5 June to 9 of June
= 9 - 5 + 1
= 5

Total number of grapefruits sold
= (4 x 52) + (5 x 22) + 82
= 208 + 110 + 82
= 400

Number of days from 1 June to 20 June
= 20 - 1 + 1
= 20

Average number of grapefruits sold
= 400 ÷ 20
= 20

Answer(s): 20