A ferry can carry a maximum of 30 adults or 35 children. A ticket for an adult cost $40 and a ticket for a child cost $30. A group of adults and children took 2 such ferries at maximum load on a ferry trip. The total amount paid for the children was $150 less than the total amount paid for the adults.

1. How many adults were there?
2. How many children were there?   

Number of adults	Amount paid for adults	Number of children	Amount paid for children	Difference in total amounts paid
60	60 x 40 = 2400	0	0 x 30 = 0	2400 - 0 = 2400
- 6		+ 7		- 450
54	54 x 40 = 2160	7	7 x 30 = 210	2160 - 210 = 1950
30		35		150

30 adults → 35 children _(÷5)
6 adults → 7 children

From every decrease of 6 adults, there is an increase of 7 children and the difference in the total amounts paid between the adults and the children will be reduced by $450.

If all 2 ferries are occupied by only adults, total number of adults
= 2 x 30
= 60

Total difference
= 2400 - 150
= $2250

Small difference
= 2400 - 1950
= $450

Number of sets
= 2250 ÷ 450
= 5

Total decrease in the number of adults
= 5 x 6
= 30

(a)
Number of adults
= 60 - 30 
= 30 

(b)
Number of children
= 5 x 7
= 35

Answer(s): (a) 30; (b) 35