QR problems

[ucla2134]

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It is from adea. I really suckssssssssssssssssssssssssssssssssssss at math.

1/ If 3 liters of 40% orange juice and 1 liter of
50% orange juice are mixed, which of the
following is the percentage of orange juice
in the mixture?
The answer is 42.5, have no idea??

2/A person travels to work at an average
speed of 40 mph, and returns home at 60
mph. Which of the following, in mph, is the
average speed for the entire trip?
answer: 48--> clueless. They do not give us time or distance, how the hell we solve it.

 

[ucla2134]

Can someone please help???😳

 

[polarmolar]

For the first one:

When mixed, they make up 75% and 25% of the total solution (i.e. 3L + 1L = 4L ... so 3L/4L = .75 and 1L/4L = .25).

So you multiply: (.75 x .4) + (.5 x .25) = .425

Multiple by 100 to get the percentage.

 

[Streetwolf]

#2 you can pick any distance you want; they all give the same answer. I recommend a multiple of both 40 and 60. Try a distance of 120 miles.

 

[keliao]

For the first one:

When mixed, they make up 75% and 25% of the total solution (i.e. 3L + 1L = 4L ... so 3L/4L = .75 and 1L/4L = .25).

So you multiply: (.75 x .4) + (.5 x .25) = .425

Multiple by 100 to get the percentage.

whre did you get 75 adn 25...how is that?

 

[polarmolar]

whre did you get 75 adn 25...how is that?

The problem says 1 Liter and 3 Liters, which are mixed to make 4 Liters total.

Now, simply divide by 4 Liters to find out what fraction of the total each is:

3L / 4L = .75

1L / 4L = .25

 

[keliao]

oh...gotcha...

 

[Tina324]

what i did for #1 is 3Lx.4=1.2L
1Lx(.5)=.5L

1.2+.5=1.7L

1.7L/4L=.42... therefore 42 percent

which is the same thing as polar molar's but diff route i guess

 

[ucla2134]

Thanks everybody!!!😀👍

 

[polarmolar]

Ucla2134, the more important question is if we can do them in < 1min

I hope so!!