On 1 April to 4 April, an average of 58 mangosteens were sold and from 5th April to 9 April, an average of 21 mangosteens were sold. $309 worth of mangosteens were sold from 10 April to 20 April. Given that a mangosteen was sold for $3, find the average number of mangosteens sold from 1 April to 20 April.
Number of mangosteens sold from 10 April to 20 April
= 309 ÷ 3
= 103

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

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

Total number of mangosteens sold
= (4 x 58) + (5 x 21) + 103
= 232 + 105 + 103
= 440

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

Average number of mangosteens sold
= 440 ÷ 20
= 22

Answer(s): 22