help for 10 points?

Question

6: A boat went 15 km upstream in the same time it went downstream 45 km. The boat’s speed in still water is 10 km/h. What is the speed of the current?
5 km/h
6 km/h
7.5 km/h
9 km/h


7: Amanda can paint a room in ten hours. Michael can paint the same room in eleven hours. How long does it take for both Amanda and Michael to paint the room if they are working together?
2 hours
3.5 hours
4 hours
5 5/21 hours


8: It takes one inflow pipe 3 hours to fill a pool, it takes another inflow pipe 5 hours to fill the same pool. How long will it take to fill the pool if the two pipes were running together?
1hours
1.5 hours
1 7/8 hours
2 2/3 hours


9: Two machines are filling soda bottles. The machines can fill the daily-quota of soda bottles in 10 hours and 15 hours, respectively. How long would it take to fill the daily-quota of soda bottles with both machines working together?
3 hours
4 hours
6 hours
8 hours


10: A gardener can trim a garden in 4 hours. An apprentice can trim the same garden in 6 hours. How long will it take to trim the garden if they both work together?
2 hours
2 2/5 hours
3 hours
3.5 hours

Answer 1

5

11*10/(11+10) = 110/21 = 5 5/21 hours

3*5/(3+5) = 15/8 = 1 7/8 hours

10*15/(10+15)= 150/25 = 6hours

4*6/(4+6) = 24/10 = 2 2/5 hours

Answer 2

This is identical to 4. (10 - x)t = 15; (10 + x)t = 45
45(10 - x) = 15 (10 + x) 20 = 4x x = 5

In each hour they paint 1/10 + 1/11 of the room. (1/10 + 1/11)t = 1; (11 + 10)t = 110; t = 110/21 = 5 5/21 hours

(1/3 + 1/5)t = 1; t = 15/(5+3) = 15/8 = 1 7/8 hours

(1/10 + 1/15)t = 1 ; t = 150/(15 + 10) = 6 hours

(1/4 + 1/6) t = 1; t = 12/(3 + 2) = 2.4 hours

Answer 3

6. Let the speed of the current be x
Since the time of boat going upstream 15km and downstream 45 km is same,
we Get this equation --(15/10-x)=(45/10+x)solving it we get x as 5. thus x=5.
7.time it will take Amanda and Michael working together will be t
therefore, 1/10+1/11= 1/t
thus, t= 5 5/21 hrs.

8. 1/3+1/5 =1/t
t=1 7/8 hrs

9.1/10 +1/15=1/T
thus, t=6 hrs

10. 1/4+1/6=1/t
thus, t= 2 2/5 hrs

Answer 4

Mathematically speaking, Amanda and Michael could probably paint the room somewhere between 10 and 11 hours if they both focused, but invariably when you get a cute girl and a guy alone in a room, she'll flirt with him, maybe unbutton a couple of buttons on her blouse, they will start making out, and the next thing you know they are having sex on the couch, which means that the room will probably not get painted at all. As for the rest of your questions, I am now so hot and bothered by the thought of Amanda and her partially-unbuttoned blouse and her perky breasts that I am not thinking about math.

Answer 5

6. Solve 15/(10 - r) = 45/(10 + r), find r = 5.

You really should do your own homework. (Where did you hide Questions 1 through 5?)