To fill a tank measuring 10 cm by 20 cm by 28 cm completely, it takes Tap B 42 minutes while it takes Tap C only 28 minutes. How long will it take to completely fill the container with water if both the taps are turned on at the same time and 6 cubic containers of edges 6 cm, filled to the brim with water are poured into the tank? Leave your answer in minutes and round off to 2 decimal places.
Volume of the tank 
= 10 x 20 x 28
= 5600 cm³
= 5600 mℓ

Volume of 6 containers
= 6 x 6 x 6 x 6
= 1296 cm³ 
= 1296 mℓ

Remaining volume to be filled by the Tap B and Tap C 
= 5600 - 1296
= 4304 mℓ
= 4304 cm³

Fraction of the tank to be filled
= ⁴³⁰⁴₅₆₀₀
= ²⁶⁹₃₅₀

Tap B:
1 tank → 42 min
1 min → ¹₄₂ tank

Tap C:
1 tank → 28 min
1 min → ¹₂₈ tank

Tap B and Tap C:
1 min → ¹₄₂ + ¹₂₈ = ²₈₄ + ³₈₄ = ⁵₈₄ tank

1 tank = ⁸⁴₅ min

²⁶⁹₃₅₀ tank = ⁸⁴₅ x ²⁶⁹₃₅₀ = ¹⁶¹⁴₁₂₅ = 12.912

Answer(s): 12.91 min