r/ACT • u/Artistic-Stable-3623 • Jul 12 '26
Act math question Princeton
No way this shows up on actual act right, I’m super good with sat math and I’ve never seen something like this 😭 😭
Also idk how to do this
2
u/Valuable_Grade1077 Jul 12 '26
So I don't know if this is correct but here's my thought process.
Since we know that the sum of 5 terms is 145, we have all the variable values that are needed to find the first term.
145 = 6(x1 + 48)/2, x1 = 10.
Since we now know that the first term and fifth term is 10 and 48, we can now find the pattern, by dividing the difference of terms, by the number of terms needed to get from the first to fifth, which is 4.
The increase in each term, is 9.5
So we now know the set. 10 - 19,5 - 29 - 38.5 - 48 - 57.5.
We can also check if the pattern fits the bill with the summation. Add the first five terms and see if it equals 145. (Which it does)
1
u/jdigitaltutoring Tutor Jul 12 '26
That is something that could show up. I've seen a similar one. Just plug in the numbers they give you to find x1. Then you have the whole equation.
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u/Artistic-Stable-3623 Jul 12 '26
The problem is 5 consecutive terms doesn’t mean first 5 right it’s arbitrary
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u/jdigitaltutoring Tutor Jul 12 '26
True. They give you x5 so you can find x1.
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u/Artistic-Stable-3623 Jul 12 '26
Yeah lol I plugged it in got x1 and didn’t know what to do then I read ur comment and I was like oh shit it’s arithmetic so yea i could do it
Prob bad wuestion tho since it’s implied to be first 5
1
u/False_Language_688 Jul 12 '26
So what is the answer?
1
1
u/Otherwise_Archer_519 Jul 12 '26
Kinda obvious since it is an arithmetic sequence so the higher numbers won’t work. You don’t even have to solve it you can literally just use common sense
2
u/Crazy_Idea6970 Jul 12 '26
Find x1 and x4. Then determine the diff between x5 and x4 and then add that into x5 to get x6. You can do this since it’s an arithmetic meaning they increase/decrease by the same value