A group of friends is addressing wedding invitations. Casey can address 20 envelopes in one hour, Anne can address 44 envelopes in two hours, and Paula can address 68 envelopes in three hours. About how long will it take them to address 400 envelopes?

Time taken = 6.2 hours

Step-by-step explanation:

Firstly, we will calculate the rate of each person per hour. Then we combine the rates and afterward divide the number of envelope they could address by the combined rate.

Casey can address 20 envelopes at the rate of 20 per hour.

Casey rate = 20 envelope per hr

Anne can address 44 envelope in 2 hours

Anne rate = 22 envelope per hr

Paula can address 68 envelope in 3 hours

Paula rate = 68/3 envelope per hr

Time it will take them to address 400 envelope can be solved below

Add their rate = 20 + 22 + 68/3 = 42 + 68/3 = (126 + 68) / 3 = 194/3

Time = 400 : 194/3 = 400 * 3/194 = 1200/194 = 6.1855670103

Time taken = 6.2 hours