It takes Faucet W 30 minutes to fill a tank measuring 15 cm by 10 cm by 11 cm completely while it takes Faucet N only 20 minutes. How long will it take to completely fill the tank with water if both faucets are turned on at the same time and 6 cubic cubes of edges 5 cm, filled with water, are poured into the tank? Leave the answer in minutes and round off to 2 decimal places.
Time taken by Faucet W to fill the tank:

30 min → 1 tank
1 min → ¹₃₀ tank

Time taken by Faucet N to fill the tank:
20 min → 1 tank
1 min → ¹₂₀ tank

Volume of the tank
= 15 x 10 x 11
= 1650 cm³

Volume of 6 cubic cubes
= 6 x (5 x 5 x 5)
= 750 cm³

Time taken by Faucet W and Faucet N to fill a tank:
1 min → ¹₃₀ + ¹₂₀ =⁵₆₀ = ¹₁₂ tank

¹₁₂ tank → 1 min
1 tank → 1 ÷ ¹₁₂ = 1 x ¹²₁ = 12 min

Remaining volume of the tank to be filled by both faucets 
= 1650 - 750
= 900 cm³

Time taken to fill the tank
= ⁹⁰⁰₁₆₅₀ x 12
= 6.5454545454545
≈ 6.55 min

Answer(s): 6.55 min