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ACT Mathematics Videos 164 videos
ACT Math: Coordinate Geometry Drill 1, Problem 1. Which inequality is expressed by the number line?
ACT Math: Intermediate Algebra: Drill 3, Problem 1. Find the fifth number in the series.
ACT Math: Pre-Algebra Drill 1.2. What proportion of Jenna's day is spent Wii-swimming?
ACT Math 3.1 Intermediate Algebra 1955 Views
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Description:
ACT Math: Intermediate Algebra: Drill 3, Problem 1. Find the fifth number in the series.
Transcript
- 00:04
Time for your daily dose of shmoop...Open wide!
- 00:07
Find the 5th number in this series: 0, -1, -3, -7...
- 00:13
And here are the potential answers...
- 00:16
OK so what is this question asking?
- 00:18
Well, there's clearly a pattern we're being asked to observe...
Full Transcript
- 00:22
And here, we get exponentially more negative as we go along. Sorta like this guy.
- 00:27
We are just being asked to find the number that comes after negative 7 and we're travelling
- 00:34
left from 0 in steps of 1, 2, then 4...
- 00:40
The pattern is "2 times... something..." Looks like 2 times the previous number, then
- 00:46
minus 1...
- 00:46
...so if we keep going, we're at minus 7 times 2 which is minus 14...
- 00:52
...then subtract 1 and we have minus 15.
- 00:56
Answer A
- 00:57
Hopefully you got that right. We don't want to take any chances at upsetting Mr. Black.
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