pre calc functions

[Saraelizabeth529]

Hi, I'm having a very hard time with these few questions and was wondering if someone could please show me the correct steps to answering them.

Jack and Phil are waxing the floor of the gymnasium , which has a surface area of 3200 square feet. Phil starts at 8:15 am and waxes 13 square feet every 2 minutes. Jack starts at 9:05 am and waxes 31 square feet every 3 minutes.
Let x equal minutes past 9.

Right now I have Y1= (13/2)x+45
Y2= (31/3)x-5

1.) At what time have they finished the floor?- So far, I added y1 and y2 together ( y3) and tried intersecting it with y5 ( 3200) but I keep getting an error on my calculator.

2.) what percentage of the floor did phil wax?

3.) At what time will Jack have waxed 112 more square feet then Phil?

 

[Denis]

I can't tell what you're doing; sorry...

Anyhow, at 9.05, Phil has waxed for 50 minutes, so left is 3200 - (50 * 6.5) = 2875 square feet
From 9.05, they work at combined speed of 6 1/2 + 10 1/3, so time to finish = 2875 / (6 1/2 + 10 1/3)

 

[nikkor180]

Let x = minutes worked beyond 9:00. Then at 9:00, Phil had already worked 45 minutes, thereby completing 45(6.5) = 292.5 ft^2. Therefore, in t minutes [after nine], Phil completes A1(t) = 6.5t + 292.5. Similarly, because Jack began 5 minutes after nine, his progress is indicated by A2(t) = (31/3)t - (31/3)*5 = (31/3)t - 155/3 ft^2. Sum A1 and A2 and set to 3200. I assume you can take it from here.

#2 is simple enough.
#3 is solved by A2 - A1 = 112

Regards,

Rich B.