Question

On an average the income for 15 days is $7, average for the first 5 days is $6 and the average for the last 9 days is $8. What is the income on the sixth day?

Answer 1

Total income in 15 days=15*7$
=105$
Also Total income
=income of 5 days + income of 6th day + income of last 9 days
=5*6$+Income of 6th day+9*8$
=30$+Income of 6th day+72$
=102$+Income of 6th day
Equating both
105$=102$ + Income of 6th day
Income of 6th day=105$-102$
=3$
Hope it helps
:)