? asked in Science & MathematicsMathematics · 9 years ago

1. Janet and experience sales clerk can fill a certain order in 6 hours. tom a new clerk needs 11 hours to do the same job. working together, how long will it take them to fill the order?

2.: a paddle boat can move at the speed of 10 km/h in still water. the boat is paddled 8km downstream in the same time it takes to go 4 km upstream. what is the speed of the river.

thanks for the help ;)

Relevance
• 9 years ago

1)

(1 / 6hours) + (1 / 11 hours) = 1 / combined time

17 / 66 = 1 / combined time

combined time = 66 / 17 = 3.88235 hours = 3 hours and 53 minutes

2) x = river speed

time = distance / speed

time1 = time2

distance1 / speed 1 = distance2 / speed2

8 / (10 + x) = 4 / (10 - x)

8(10 - x) = 4(10+x)

80-8x = 40+4x

40 = 12x

x = 3.33 km/hr

• DOVE
Lv 6
9 years ago

1. Janet and experience sales clerk can fill a certain order in 6 hours. tom a new clerk needs 11 hours to do the same job. working together, how long will it take them to fill the order?

Janet an experience sales clerk can fill a certain order in 6 hours

Janet's one hr work= 1/6

tom a new clerk needs 11 hours to do the same job.

Tom's one hr work= 1/11

Both's one hr work= 1/6 +1/11= 17/66

Boyh will fill a certain order in 66/17 hours

2.: a paddle boat can move at the speed of 10 km/h in still water. the boat is paddled 8km downstream in the same time it takes to go 4 km upstream. what is the speed of the river.

Let the speed of the river= x kmph

Upstream speed= 10-x

Downsream speed= 10+x

the boat is paddled 8km downstream in the same time it takes to go 4 km upstream.

Time the boat is paddled 8km downstream =time it takes to go 4 km upstream.

8/(10+x)=4/(10-x)

2/(10+x)=1/(10-x)

2(10-x)= 10+x

20-2x= 10+x

3x=10

x=10/3 kmph

• David
Lv 7
9 years ago

x[(1 / 6) + (1 / 11)] = 1

x[(11 + 6) / 66] = 1

x(17/66) = 1

x = 66/17 hours

3 15/17 hours

x(10 + y) = 8

x = 8 / (10 + y)

x(10 - y) = 4

x = 4 / (10 - y)

8 / (10 + y) = 4 / (10 - y)

8(10 - y) = 4(10 + y)

80 - 8y = 40 + 4y

40 = 12y

40/12 = y

3 1/3 kph = y

• 9 years ago

1. 6+11=17/2=8.5 hours

2. 6km/h

I think haha