one clerk can stuff every 30 seconds the 2nd clerk i every 40 seconds. how long will it take them to stuff 140 envelopes
1/30 = .033 envelopes/sec
1/40 = .025 envelopes/sec
so
.033+.025 = .058 envelopes /sec together
1/.058 = 17.2 seconds/envelope
140 envelopes * 17.2 seconds/envelope = 2413 seconds or 40 minutes
To solve this problem, we can calculate the combined rate at which both clerks stuff envelopes and then divide the total number of envelopes by this rate.
Let's assign the rate of the first clerk as "1 envelope/30 seconds" and the rate of the second clerk as "1 envelope/40 seconds".
Now, to find the combined rate, we add the rates of both clerks:
Combined rate = 1/30 + 1/40
To simplify this, we need to find a common denominator:
Combined rate = (4/120) + (3/120)
= 7/120
So, the combined rate at which both clerks stuff envelopes is 7/120 envelopes per second.
To find the time it takes to stuff 140 envelopes, we divide the total number of envelopes by the combined rate:
Time taken = 140 / (7/120)
To divide by a fraction, we multiply by the reciprocal:
Time taken = 140 * (120/7)
= 2400/7
Therefore, it will take them approximately 342.86 seconds to stuff 140 envelopes.