Question

A water tank had three inlets, which independently can fill the tank in 20, 40 and 30 minutes, respectively. How much time does it take to fill the tank when all three inlets work together?


with method​

Answer 1

Let Inlet A fill the tank in 20min. , inlet B fills the tank in 40 min. , inlet C fills the tank in 40 min. Then
Taking LCM of all three we get 120
In 1 hour the amount all 3 tanks will fill is
A=120/20=6ltr
B=120/40=3ltr
C=120/30=4ltr
Adding all these they fill 13 ltr in total
If they work together, divide lcm by total ltr.
120/13 minutes

Answer 2

Answer:  it will take 120/13 minutes = 9.23minutes

Step-by-step explanation:

In this type of questions we first get the filling in 1 minute for pipes then we will add them to get the result, as

Part filled by A in 1 min = 1/20

Part filled by B in 1 min = 1/40

Part filled by C in 1 min = 1/30

Part filled by (A+B+C) in 1 min = 1/20 + 1/30+1/40

= 13/120

So all pipes can fill the tank in 120/13 mins.=9.23 min

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