frindle2
Member
- Joined
- Sep 22, 2013
- Member Type
- Other
- Native Language
- Korean
- Home Country
- South Korea
- Current Location
- South Korea
Hello. What does "None" mean of choice (d)?
Does it mean "it's impossible to calculate"? Thank you.
--------------------from Dare to Disappoint by Ozge Samanci
A swimming pool can be filled by Valve X in 6 hours.
When the swimming pool is full, Valve Y can drain half of the pool in 9 hours.
Valve Z can drain the entire pool in 10 hours.
If the swimming pool is empty, how many hours will it take
to fill the pool with all three valves open?
(a) 6 (b) 5 (c) 7 (d) None
Does it mean "it's impossible to calculate"? Thank you.
--------------------from Dare to Disappoint by Ozge Samanci
A swimming pool can be filled by Valve X in 6 hours.
When the swimming pool is full, Valve Y can drain half of the pool in 9 hours.
Valve Z can drain the entire pool in 10 hours.
If the swimming pool is empty, how many hours will it take
to fill the pool with all three valves open?
(a) 6 (b) 5 (c) 7 (d) None