Apps. and Interpretation for IBDP Maths Ebook 1 | Page 57

15
Paper 1 – Systems
Example
3000 citizens attended a carnival. Let x be the number of adults attending the carnival
and y be the number of children attending the carnival.
(a) Write down an equation in x and y .
The cost of an adult ticket and a child ticket were set to be USD 18 and USD 8
respectively. The total cost of tickets sold in the carnival was USD 36000.
(b) Write down another equation in x and y .
(c) Write down the values of x and y .
(d)
Find the total cost for a group of 4 adults and 7 children.
[1]
[1]
[2]
[2]
6
Solution
(a) x�y� 3000
A1 N1
(b) 18x�8y� 36000
A1 N1
(c) x � 1200 , y � 1800
A2 N2
(d)
The total cost
�18(4) � 8(7)
(M1) for substitution
� USD 128
A1 N2
[1]
[1]
[2]
[2]
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