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| 1. | 120 bags of half litre milk can be filled by a machine within 3 minutes find the time to fill such 1800 bags? | 
| Answer» Let b represent the number of bags of half litre milk and t represent the time required to fill the bags. Since, the number of bags and time required to fill the bags varies directly. ∴ b ∝ t ∴ b = kt …(i) where k is the constant of variation. Since, 120 bags can be filled in 3 minutes i.e., when b = 120, t = 3 ∴ Substituting b = 120 and t = 3 in (i), we get b = kt ∴ 120 = k × 3 ∴ k = 120/3 ∴ k = 40 Substituting k = 40 in (i), we get b = kt ∴ b = 40 t …(ii) This is the equation of variation. Now, we have to find time required to fill 1800 bags. ∴ Substituting b = 1800 in (ii), we get b = 40 t ∴ 1800 = 40 t ∴ t = 1800/40 ∴ t = 45 ∴ 1800 bags of half litre milk can be filled by the machine in 45 minutes. | |