A can type 100 letters in 5 minutes. B and C typing together can type ...
A can type 20 letters in one minute
B and C can can type 25 letters in one minute
A,B and C together can type 45 letters in one minute
45 letters in 1 minute
so 90 letters in 2 minute.
A can type 100 letters in 5 minutes. B and C typing together can type ...
Given:
A can type 100 letters in 5 minutes.
B and C typing together can type 50 letters in 2 minutes.
To find:
If all of them working together then can type 90 letters in how many minutes?
Solution:
Let the efficiency of A, B, and C be a, b, and c respectively.
According to the question,
A can type 100 letters in 5 minutes.
Therefore, the efficiency of A, a = 100/5 = 20 letters per minute.
B and C typing together can type 50 letters in 2 minutes.
Therefore, the efficiency of B and C, b + c = 50/2 = 25 letters per minute.
Let's assume that all three work together for x minutes to type 90 letters.
Therefore, the total number of letters typed by A, B, and C working together is 90.
So, we can write the equation as:
20x + 25x = 90
45x = 90
x = 2
Therefore, all three working together can type 90 letters in 2 minutes.
Hence, the correct answer is option A) 2 minutes.