thanks a lot. It took me a lot of years before I learn how to solve these problems.

@MrB4math

5 жыл бұрын

You are welcome, and thanks for the comment.

You did the last one right. It was 28 mph in still water and add 7 for downstream and subtract 7 of upstream. Good job bro. I know its now 10 years later and you probably don't care. LOL

Excellent

@MrB4math

5 жыл бұрын

Thanks for the comment and the compliment.

Wouldn't it have been much easier to continue with the approach of having three categories in the fourth problem (e.g., "upstream", "downstream", and "still water")??

and 1/7 time x beacuse we know there rate but we want to know per how much time that will give us the amount of work each of them were doing

@MrB4math

6 жыл бұрын

It seems to me we want the total time to paint if they work together. What we need to tackle this problem is a true mathematical statement involving one variable, then we let the math take care of the rest. There may be other approaches that generate the correct answer; this happens to be the approach with which I am familiar. I wish I could be more helpful, but writing is a hard way to communicate on math problems like this.

I don't understand why with the boat question it is x-7 when it doesn't say anything about it being slower or decreasing.

@MrB4math

6 жыл бұрын

Tasha Mac That's a good question. When the boat goes upstream, it's speed X is slowed by the 7 mph current that it must fight against. That gives us x-7. Notice that when the boat goes downstream, the current helps it to go faster by 7mph, so we get x+7 for the downstream part of the trip. I hope this helps. Mr. B.

@tashamac7300

6 жыл бұрын

MrB4math OK. It did. Thank you. Watching your other videos now👍

@MrB4math

6 жыл бұрын

I should have said kilometers per hour, not miles per hour, sorry.

@tashamac7300

6 жыл бұрын

MrB4math it's all good. I'm studying for the GACE teacher certification exam and this is helping a lot. Thanks.

confusion here shouldnt the total equal 1 we want to know how long it will take them to complete the job not to get part of the job done

@MrB4math

6 жыл бұрын

Do you mean the total time? The total time will equal some number of hours, which in this case appears that it will be more than one hour. The "total job" can be thought of as a 1, as in 1 complete job.

Confused

Where do you get these word problems from?

@MrB4math

4 жыл бұрын

These came from an introductory algebra textbook.

@yallseeyeah

4 жыл бұрын

MrB4math do you know name of the book? Thank you

So whats the answer in still water???

@MrB4math

6 жыл бұрын

Sorry about that, as I was not very clear at all. The rate in still water is the x value of 28 kilometers per hour.

@kozuta8858

6 жыл бұрын

@@MrB4math ty now i get it because it says same amount of time that means 28-7=21 then 28+7=35 and then to find time we divide distance to rate so 9÷21 is 0.43 and 15÷35 is 0.43 as well thanks

I think it is simpler than this but only because of your help. You add the two painters time (16 hours) and divide it by 2 (8 hours). That gives you the average amount of time it would take them to complete two houses together in two hours since one of them can each do one house alone in 1 hour. Then you divide that amount of time by 2 (4 hours), since two people will be working on just one house in half the time, we want to know half, which gives you 4 hours since they will be painting one house in just one hour and not two, that will give you half. I am never right on these, just close. The teacher is always right. You did not give the final answer so I would like to know if I am correct....The very last one, if t1=t2 = 28 hours, d2 does not equal d1, d2-d1 must equal the amount the boat moves in still water = 6km, r = d/t = 6km/28hrs....6 km in 28 hours; or 3 km in 14 hours; or 1.5 km in 7 hours. Am I right or wrong? Please clarify. I will delete my comment after correction.

Problem 9: 9/7=1.285, 7/7=1, 1+1.285=2.285, 9/2.285=3.93 hours or 3 hours 55 minutes.

Shortcut to the first problem: (7 x 9)/(7 + 9) = 63/16. Shortcut to the second problem: ((12)(x))/(12 + x) = 6 --> x = 12