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ACT Math: Pre-Algebra Drill 1.2. What proportion of Jenna's day is spent Wii-swimming?
ACT Math: Pre-Algebra Drill 5, Problem 5. How many red cards must be added so that the proportion of red cards is one half?
This video covers how to use cross products to solve for a missing number in a proportion by setting that proportion with a variable over the produ...
ACT Math 5.5 Pre-Algebra 347 Views
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Description:
ACT Math: Pre-Algebra Drill 5, Problem 5. How many red cards must be added so that the proportion of red cards is one half?
Transcript
- 00:03
Here's your shmoop du jour:
- 00:05
A box of cards contains 23 red and 30 black cards. Must have been made in China.
- 00:10
How many red cards must be added so that the
- 00:13
proportion of red cards is 1/2?
- 00:16
And here are the potential answers...
Full Transcript
- 00:22
So... we're not dealing with a standard deck of playing cards. Kind of hard to play
- 00:25
"Go Fish" with only one eight.
- 00:27
Okay, so here's a scale: 23 cards on the left -- red ones; 30 cards on the right -- black ones.
- 00:34
To get the red cards to be half of the total, or equal to the black cards...
- 00:39
...we need to have just as many of them as we have black cards.
- 00:43
We can just add 7 of 'em, and then we'll have 30 of each.
- 00:47
And that's all there is to it. Answer: D.
- 00:49
As in, "Deck of Card."
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