Amy and Bob decide to paint one wall of a building. Working alone, Amy takes 12 hours to paint the entire wall while Bob takes 18 hours for the same. Amy painted the wall for 4 hours and then Bob took over and completed the wall. How long did it take for them to paint the entire wall
From the above question, we are given the following information
For one wall, working alone,
Amy can paint for 12 hours
Which means, in
1 hour , Amy would have painted = 1/12 of the wall
Bob can paint for 18 hours
Which means ,
in 1 hour, Bob would have painted = 1/18 of the wall.
We are told Amy painted the wall for 4 hours and then Bob took over and completed the wall.
Find the portion of the wall Amy painted before Bob took over.
Amy painted the wall for 4 hours before Bob took over.
1 hour = 1/12 of the wall for Amy
4 hours =
4 × 1/12 ÷ 1
= 4/12 = 1/3
Amy painted one third(1/3) of the wall
Find the number of hours left that Bob used in painting the remaining part of the wall
Let the entire wall = 1
If Amy painted 1/3 of the wall
Bob took over and painted = 1 - 1/3
= 2/3 of the wall
Bob painted 1/18 of the wall = 1 hour
2/3 of the wall = ?? = Y
2/3 × 1 = 1/18 × Y
Y = 2/3 ÷ 1/18
Y = 2/3 × 18/1
Y = 36/3
Y = 12 hours.
This means, the number of hours Bob worked when he took over from Amy = 12 hours.
The third and final step is to calculate how many hours it took them to paint the wall
Number of hours painted by Amy + Number of hours painted by Bob
= 4 hours + 12 hours
= 16 hours
Therefore, it took them 16 hours to paint the entire wall.
3. is B
6. is A
8. is C D
3. I don't see any dialogue
6. not sure
8. I think B
I would say 4.
Often, the misconception for average speed is that we get the average of the two speeds given when inf act we have to divide the total distance by the total time. We can also make use of the distance, rate and time formulas.
Average Speed = Total Distance / Total Time
Distance = Rate * Time
Rate = Distance / Time
Time = Distance / Rate
Take note that the distance that she traveled going to and from the home is the same. So the distance uphill and downhill is just the same. Don't forget to convert the time we have into minutes for the units to be compatible.
18 minutes = 18/60 hours = 3/10 hoursFirst, let's get the total distance.
Distance = 20 miles per hour * 3/10 hours
Distance = 6 miles
Total Distance = 2 * 6 miles = 12 milesNext, get the total time.
Time = 6 miles / 60 mph
Time = 1/10 hour
Total time = 3/10 hour + 1/10 hour = 2/5 hour.Combine the two values.
Average speed = 12 miles / (2/5) hour
= 12 * (5/2)
= 30 mph
Therefore, her average speed is 30 mph.
20+60= 80 divided by 2
Explanation is in a file
it would take chad 8.1 hours to paint the fence on his own