Question
Varun and Arnav can finish a work in 28 days and 56 days
respectively when working alone. Varun starts first. In how many days should Arnav join him so that the entire job finishes in 21 days?Solution
ATQ,
Let the total work be 56 units (LCM of 28 and 56)
Efficiency of Varun = (56 / 28) = 2 units/day
Efficiency of Arnav = (56 / 56) = 1 unit/day
Let Arnav join after 'n' days.
So, 2n + (2 + 1) × (21 - n) = 56
⇒ 2n + 63 - 3n = 56
⇒ n = 7
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