Problem Solving (PS) | Re: Tina can do a piece or work in 15 days, whereas Mina can do the same p

let the total work be 60 units (LCM of 20 and 15)
tina's efficiency per day = 60/15 = 4
Mina's efficiency per day = 60/20 = 3
Tina and mina working together for 7 days = 7* 7 =49
work left 11 units
Mina working alone 11/3 = 3.66 days required
Hence answer is A

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