Question

Ganga and Saraswati, working separately can mow a field in 8 and 12 hours respectively. If they work in stretches of one hour alternatively. Ganga beginning at 9 am, when will the mowing be completed? 

(a) 6 p.m. 

(b) 6.30 p.m. 

(c) 5 p.m. 

(d) 5.30 p.m.

Answer 1

Correct option (b) 6.30 p.m.

Explanation:

According to question, 

Ganga begins at 9 am and she does 3 units/hours Saraswati begins at 10 am and she does 2 units/hours So by 11 am they complete 5 units

And now Ganga will complete 3 unit out of 4 units in 1 hr Now,

Rest 1 unit work done by Saraswati in = 1/2 hr