Student A, B and C con complete a puzzle in 20 min, 15 min, and 30 min respectively. If all three student work together, how long will it take to complete the puzzle?
use the same method I just showed you in your previous post.
Let me know what you got.
1/20 + 1/15 + 1/30 = 3/60 + 4/60 + 2/60 = 9/60
0.15 = 15 min
I think is wrong?
You followed my steps only up to a point
combined rate = 9/60 ---- correct
time at combined rate = 1/(9/60) = 1 ÷ (9/60)
= 1 (60/9)
= 60/9 = 15 minutes
You just divided 9 by 60 to get .15
and it is just coincidence that the digits of .15 and the correct answer of 15 are the same
To find out how long it will take for all three students to complete the puzzle when working together, you need to calculate their combined work rate.
The work rate of a student is determined by the amount of work they can complete in a given time period. In this case, we can determine the work rates of students A, B, and C by calculating the reciprocal of the time it takes for each student to complete the puzzle.
The work rates are as follows:
Student A: 1 puzzle / 20 min = 1/20 puzzle/min
Student B: 1 puzzle / 15 min = 1/15 puzzle/min
Student C: 1 puzzle / 30 min = 1/30 puzzle/min
To find the combined work rate of all three students, you simply add up their individual work rates:
Combined Work Rate = 1/20 + 1/15 + 1/30
To simplify this expression, you can find a common denominator of 60:
Combined Work Rate = (3/60) + (4/60) + (2/60) = 9/60 = 3/20 puzzle/min
Now that you know that their combined work rate is 3/20 puzzle per minute, you can determine how long it will take for them to complete the puzzle by taking the reciprocal of the combined work rate:
Time to Complete the Puzzle = 1 / (3/20) = 20/3 min ≈ 6.67 min
Therefore, when all three students work together, it will take approximately 6.67 minutes to complete the puzzle.