Help Plz (1 Viewer)

[ahohen_77]

hey im in yr 11 and need help in some qs from the cambridge textbook, :

1.a certain tank can be filled by two pipes in 80 minutes. the larger pipe by itself can fill the tank in 2 hours less than the smaller pipe by itself. How long does each pipe take to fill the tank on its own?

2. a certain tank has an inlet valve and an outlet valve. the tank can be filled via the inlet valve in 6 minutes and emptied(from full) via the outlet in 10 minutes. If both valves are running at the same time, how long would i take to fill the tank up if it was empty to begin with?

oh and is there anyone here who i can constantly ask 2/3 unit maths questions, thus i wouldnt have to persistently start new threads, coz my teacher teaches really fast and this cambridge textbook is insane

 

[Affinity]

let the capacity of the tank be C
let the rate water inflow from the 2 taps be L and S respectively

we have
(L+S)*80 = C
C/L = C/S - 120

80(L+S)/C = 1
C(L - S) = 120 LS

80(L^2 -S^2) = 120 LS

solving, L = 2S

so the smaller pipe takes 240 mins
and the larger pipe than 120 mins

2.)
rate inlet = + 1/6 tank/min
rate outlet = - 1/10 tank/min
combined rate = 1/6 - 1/10 = 1/15 tanks per min..

so it takes 15 mins

you best bet is the post questions here or the 3 unit forum.. usually someone will answer it within an evening