A group of friends is addressing wedding invitations. Casey can address 23 envelopes in one hour, Anne can address 45 envelopes in two hours, and Paula can address 61 envelopes in three hours. About how long will it take them to address 310 envelopes?

"4.71" is the correct answer.

Step-by-step explanation:

As we know, 45 envelopes addressed in 2 hours then,

⇒  

and, 45 in 3 hours,

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Now by adding all together, we get

⇒  

⇒  

and multiply it by "4.71", we get

⇒  

⇒  

Round it "310".

So that "4.71" is the right answer.

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