Question 912726
r*t=d
(r-10)*t=440
(r-10*t=440
r*t-10*t=440

(r+10)*t=495
r*t+10*t=495
r*t-10*t=440
add
2r*t=935
r*t=935/2
r*t=467.5
ok
r*t-10*t=440
467.5-10*t=440
467.5-440=10*t
27.5=10*t
27.5/10=t
2.75=t
t=2.75 hour time
r*2.75=467.5
r=467.5/2.75
r=170.0 mph rate still air
check
(r+c)*t=495
(170+10)*2.75=495
(180)*2.75=495
495.0=495

(r-c)*t=440
(170-c)*t=440
(170-10)*2.75=440
160*2.75=440
440.0=440
ok