A system of equations is a set of equations that share the same unknowns and must be true at the same time.
Many SHSAT problems in this topic are word problems about two kinds of things, such as tickets at different prices or coins of different values, with a total count and a total value given. One equation counts the items and the other adds up their value.
Systems of equations can be solved by substitution or elimination, and a quick check is to imagine every item is the cheaper kind and see how far the total falls short. Averages can also hide a system.
Sample questions
Pick an answer to see whether it is right — nothing is saved, and nothing needs an account.
Question 1Mid
At a school event, adult tickets cost 6 dollars each and student tickets cost 4 dollars each. A total of 58 tickets were sold for 276 dollars. How many adult tickets were sold?
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Answer: D — 22
If all 58 tickets had cost $4, the total would have been 232. The actual total was 276, which is 44 more. Each adult ticket adds 2 more than a student ticket, so 44÷2=22 adult tickets were sold.
Question 2Mid
A playlist has 14 training videos. Each short video is 3 minutes long, and each long video is 5 minutes long. The total running time is 54 minutes. How many long videos are in the playlist?
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Answer: B — 6
If there are l long videos, then there are 14−l short videos. The total time is 5l+3(14−l)=54. This gives 5l+42−3l=54, so 2l=12 and l=6.
Question 3Mid
In a club of 25 students, each student sold either 2 raffle tickets or 5 raffle tickets. The average number of raffle tickets sold per student was 3.2. How many students sold 5 raffle tickets?
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Answer: D — 10
The total number of tickets sold was 25⋅3.2=80. If x students sold 5 tickets, then 25−x students sold 2 tickets, so 5x+2(25−x)=80. This gives 3x+50=80, so x=10.
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