Question

5 men can do a work in 6 days in how many days 15 men can do the same work

Answer 1

$5 : 6 : : 15: x \\ product \: of \: mean = product \: of \: extreme \\ 6x = 5 \times 15 \\ x = 5 \times 15 \div 6 \\ x = 16.5$

Answer 2

5 men=6days
1 man=6/5day
15men=6/5×15
18days
15 men can do the same work=18days