Answer:
4 hours 7 minutes
Step-by-step explanation:
Since Trevon takes 10 hours to clean the attic, he cleans 1/10, 10% or .1 of the attic per hour. Since Cody takes 7 hours to clean the attic, he cleans 1/7, 14.3% or .143 of the attic per hour.
Together, that means they clean .1 + .143 of the attic per hour. That's an hourly rate of:
.1 + .143 = .243
The portion of the attic they clean in x hours is .243x. We'd like to know how long it will take them to clean 100% or 1 of the attic. So:
.243x = 1 Divide each side by .243
x = 1/.243
x ≈ 4.115
Let's convert .115 to minutes by multiplying by 60
.115 * 60 = 6.9 round to 7 for 7 minutes
It will take them around 4 hours 7 minutes to clean the attic.
